Good day
Before answering this specific question I believe we need to take a look at a few ways that people are influenced (regardless of whether it's positive or negative)
By family and friends - The opinions of our family and friends may have influenced us in making certain decisions on various things and that may still be the case today. We may also find that our views and opinion on certain subjects, as well as certain habits, were influenced by their opinions.
School teachers/lecturers, religious groups as well as the media (the news, TV series, movies, articles posted on the internet, You Tube videos, magazines, chat groups, blogs, etc.) - have all shaped our thinking and opinion on things in one way or another and influenced our decisions.
Our environment - An example here is where a child grows up in a community where drugs, gangsterism and domestic violence is seeing as the norm and therefore conforming to these things is seeing as an "acceptable" option/decision for them to take. Another example is working in an environment where the rest of the team, as well as the manager, may be lazy and how that may influence an individual to perform likewise. The point here is how being in a particular environment can influence our behaviour and decisions.
The end result is that regardless of which way it happens, our way of thinking/outlook towards something, as well as our behaviour, decisions and actions can all change as a result of being influenced by others. We must however note that even though this is the case we are still ultimately responsible for our actions.
Now the good news is that even though we may not be able to change the fact that we will be influenced, we can try and manage what we allow ourselves to be influenced by. The reality is that we want to be influenced ... but by the right sources.
In the below passage Jesus speaks about our hearts being like soil and how when the Word is sown, the type of soil determines whether there'll be a productive harvest or not. What we find here is that the soil is always looking to produce but if the soil is not well kept it can become contaminated, and as a result, God's word struggles to bear fruit in that person's life. The important thing here is to maintain the soil and watch over it so that the right seeds produce the harvest we want to see.
Mark 4:14-20
The sower sows the Word. The ones along the path are those who have the Word sown [in their hearts], but when they hear, Satan comes at once and [by force] takes away the message which is sown in them. And in the same way the ones sown upon stony ground are those who, when they hear the Word, at once receive and accept and welcome it with joy; and they have no real root in themselves, and so they endure for a little while; then when trouble or persecution arises on account of the Word, they immediately are offended (become displeased, indignant, resentful) and they stumble and fall away. And the ones sown among the thorns are others who hear the Word; Then the cares and anxieties of the world and distractions of the age, and the pleasure and delight and false glamour and deceitfulness of riches, and the craving and passionate desire for other things creep in and choke and suffocate the Word, and it becomes fruitless. And those sown on the good (well-adapted) soil are the ones who hear the Word and receive and accept and welcome it and bear fruit—some thirty times as much as was sown, some sixty times as much, and some [even] a hundred times as much.
This is further confirmed in the following passages where we see that we cannot change the fact that our "soil" is constantly looking to produce. This isn't the problem, the problem is the seeds we allow to enter in and take root, that firstly, affects the condition of our soil, and secondly, produces a harvest that is contrary to what God wants for us ... Again, while we cannot change the fact that we will be influenced, we can try and control who or what is trying to influence us.
Luke 6:43-45
“No good tree bears bad fruit, nor does a bad tree bear good fruit. Each tree is recognized by its own fruit. People do not pick figs from thornbushes, or grapes from briers. A good man brings good things out of the good stored up in his heart, and an evil man brings evil things out of the evil stored up in his heart. For the mouth speaks what the heart is full of.
Proverbs 4:23
Keep and guard your heart with all vigilance and above all that you guard, for out of it flow the springs of life.
Galatian 6:7-8
Do not be deceived, God is not mocked; for whatever a man sows, that he will also reap. For he who sows to his flesh will of the flesh reap corruption, but he who sows to the Spirit will of the Spirit reap everlasting life.
The Bible also tells us very specifically in the below passages to guard ourselves against the wrong influences (and also tells us what we should be focusing on)
Psalm 1:1-3
Blessed is the man who walks not in the counsel of the ungodly, nor stands in the path of sinners, nor sits in the seat of the scornful; but his delight is in the law of the Lord, and in His law he meditates day and night. He shall be like a tree planted by the rivers of water, that brings forth its fruit in its season, whose leaf also shall not wither; and whatever he does shall prosper.
1 Corinthians 15:33
Do not be misled: “Bad company corrupts good character.”
Joshua 1:8
Keep this Book of the Law always on your lips; meditate on it day and night, so that you may be careful to do everything written in it. Then you will be prosperous and successful.
Philippians 4:8
Finally, brethren, whatever things are true, whatever things are noble, whatever things are just, whatever things are pure, whatever things are lovely, whatever things are of good report, if there is any virtue and if there is anything praiseworthy—meditate on these things.
Now coming back to the specific question of how often we should be reading the Bible; In the above passages (Joshua 1:8 and Psalm 1:1-3) it says very clearly to meditate in the law (word) day and night ... I'd like to explain it this way in the context of influence:
In the above examples (about family and friends, school teachers, media and our environment); in all of these instances, influence happened as a result of time spent with those person/s or media platforms.
When we spend enough time with them, we allow ourselves to receive their opinion/perspective, we latch onto their phrases or gestures or way of doing certain things, we may even copy certain words that they use (husbands and wives or best friends could probably relate best to this). If we spend enough time listening to a particular genre of music, it can influence our emotions. Constantly reading news articles on a particular subject also has a way of influencing our outlook towards something. Working in a negative environment long enough can drain and affect us negatively ... the point i'm making here is that it took time for us to be influenced - it wasn't instant - and that it'll take time, time in God's presence (in worship, prayer, reading His word, attending church, watching teachings, reading books, being around good Christian friends or family, etc.) that'll produce fruit in our lives in accordance with His word.
Now of course we will spend time with people, watch movies, read articles, etc. where they may see things differently compared to the Bible (to escape that would mean to leave this planet). Therefore in the context of influence, we cannot escape the wrong influences from coming our way but we do have a responsibility to safeguard ourselves against what we allow to enter our hearts/minds because as we read above in Galatians 6:7-8, we reap what we sow. This helps us to understand why the Bible says day and night because consider everything else that we're exposed to throughout the day in terms of what is being broadcast on TV or on social media, etc. and how much of that enters our hearts/minds in contrast to how much time we spend meditating on the word of God. It is our responsibility, in the midst of a world of contrary beliefs and agenda's, to sow the right seed into our lives, and into the lives of others, and a good starting point to all of that is to read the Bible ...
Romans 12:2
Do not be conformed to this world (this age), [fashioned after and adapted to its external, superficial customs], but be transformed (changed) by the [entire] renewal of your mind [by its new ideals and its new attitude], so that you may prove [for yourselves] what is the good and acceptable and perfect will of God, even the thing which is good and acceptable and perfect [in His sight for you].
2 Timothy 3:16-17
All Scripture is given by inspiration of God, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness, that the man of God may be complete, thoroughly equipped for every good work.
Amen