You should have a long-term plan to invest in Bitcoin so that you can grow your wealth, but we can never determine the value of Bitcoin, however, if you have money left over from your income source after meeting the needs of your family, you can invest in Bitcoin regularly or weekly or monthly according to your ability. In this way, if you continue to invest for a long time, your investment will start to grow stronger.
Consider Bitcoin investment as a type of savings, which can be called Bitcoin savings. Set a goal and keep chasing that goal consistently. How long your savings journey will be depends on your goal, but at least keep saving for a cycle (4 years). There is no specific time limit on how long you can extend it, in this case you have to prioritize your goal. It is your sole decision whether to extend your savings journey or stop after achieving the goal. One thing that is advisable is that never sell the entire investment.
If you perceived bitcoin as a form of savings then you should know that savings is a life time goal and not just a few years goal hence if you consider bitcoin investment as your savings then you will probably deep hands into your savings to save yourself in days you need urgent money, hence making bitcoin investment you can consider it a life time savings that you would keep stacking up till a very large number of years, however at the same time, before you go for the goal of bitcoin as life time investment you should also make sure you have some kind of emergency funds or reserve funds to keep you going on days that might feel tempting to deep hands into your bitcoin investment.