For example, this month I have an income of around $300 a month and I spend $200 for personal needs and around $50 to buy bitcoin. I will make different notes for investments where indeed in the ledger the financial records will definitely remain $250 as this month's expenses but when talking about bitcoin we definitely need another record where there must be a record in the expenses we make for the purchase of bitcoin so that we know how much we have spent on bitcoin while we are here and that in my opinion is important as a consideration and as a belief that in the end being in bitcoin is profitable so that we don't not know how much of our money we spend on bitcoin and how much profit we can take.
But indeed in the end maybe this depends on what we are comfortable doing because the most important thing in this case is that we don't mess around with the way we manage money regardless of the different ways that are done and the mention of something in the end the goal remains the same, namely bitcoin investment.
In your example, if a guy is buying bitcoin with 25% of his expenses (50/200), then after about 4 years, the guy would have invested a whole year's worth of his expenses into bitcoin.. .So that would not be a bad place to be in terms of building a BTC holdings that has greater chances of getting him to fuck you status or some kind of a status in which he can start to employ sustainable withdrawal.
I wonder how important your ideas about profit taking is? Sure we want to be in profits or even presume ourselves to be in profits with the passage of time, yet if the guy in your example continues with his practice of investing 25% of his expenses into bitcoin per year for 12 years, he has therefore invested 3 years worth of his expenses into bitcoin at the 12 year mark. So then maybe the other question might be how bitcoin ended up performing over that time in order to allow the amount invested to grow at least with the cost of living increases and perhaps more than that. ... even though there are no guarantees...
So I am not necessarily going to presume regarding how much profits the guy might be in, yet I would suggest that the value of his holdings may well help to guide him in regards to whether he needs to continue to invest/accumulate bitcoin or if he might bd ready to start to employ some other strategies that might either be just maintenance or perhaps getting into various kinds of withdrawal practices, whether that would be time-based withdrawals and/or raking kinds of strategies.
Surely we make our own assessments regarding where we are at and how we might want to replace and/or supplement our income with bitcoin withdrawals if we happen to get ourselves into such a position.
In addition, returning to the initial discussion about capital in the end this is also important because investment can also be a business and we must know how much we spend on accumulating bitcoins that we buy from the beginning to a certain extent consistently and how much profit we get after we invest in that period of time. It becomes an important part because after all we are in bitcoin is for profit and financial freedom so the profit factor even though it is only a figurative expression because the bitcoin remains the same only the value is different must still be considered.