He calculates out the amount that he has to set aside for his expenses, and then he attempts to maximize his BTC buys with whatever he has available, and sure sometimes the amounts might be regular and weekly or every couple of weeks, but every once in a while he might receive amounts that are way larger than his regular amount, so perhaps every week he is getting around $10 extra that he can spend on BTC, but every 3-4 months he has some side project that he receives somewhere between $150 and $300 - depending on details of how the project ended up going, so at that time, when he gets those larger payment amounts, he suddenly has 15x to 30x his usual weekly DCA amounts, so he knows that he could still choose to treat the amount as a DCA amount and buy right away, even though he also knows that when he gets those larger amounts, he has more options during the times that he ends up receiving those larger than usual amounts.
That's the strategy we have to adopt, specially the one who dont have huge cash in the form of lump sum but have some extra cash occasionally. As long as you don't have enough Bitcoin be bullish in putting anything you have in Bitcoin. I have shared my personal experience of how HODLing Bitcoins for less then a year can be helpful. If Bitcoin can increase it's value considerably in one year then how much benefit it will give in next 10 to 15 years? For that we need to go bullish in accumulating Bitcoins.
From time to time, there are still going to be some strange situations that end up happening in terms of guys sometimes forgetting about their BTC or even forgetting how to access it.. and then maybe remembering at some later point...... .so even a person might buy a few hundred dollars worth of bitcoin, and then maybe the price goes up 8x or more, so the guy goes to try to figure out how to access his BTC, but he cannot figure it out, and then maybe the price drops back down, so then he thinks that he will just get back to the problem of trying to access his coins later, and maybe he keeps procrastinating because he is not even sure he can figure it out, and maybe the BTC price goes up again, and then it is 20x or more higher than his earlier price, so then he becomes even more inspired to try to figure out how to access his coins.. and yeah, maybe it sounds weird.. but there can sometimes be weird kinds of situations that may also relate to a person who has a variety of other things going on in their lives and maybe even some explanation why they are not putting more effort into monitoring and/or managing their BTC in a more reasonable (or normal) way.
There are many such examples in initial days of Bitcoin, when people got whole bunch of Bitcoins for just few dollars or even for free. In those early days people mostly take Bitcoin for granted and they woke up when there few dollars worth of Bitcoins were in millions but they don't know how to access them. Anyone who is doing such silly mistake today must be tagged as a fool. Because of the previous cases, we must be aware that Bitcoin today will have it's value increased in coming years. To get benefit of your current hodlings in future, one must has to take care of his Bitcoins keys/passwords.