If an investor is strictly investing in bitcoin with his discretionary income, he is free to invest in bitcoin with all his discretionary income if he chooses to do that, and he will not have any problem in solving his living expenses because discretionary income is meant to be used and paid for non-important items like vacation. Any financial crisis that happens after you have paid for your monthly expenses should be treated as an emergency because you don't plan for it, and you can freely depend on your emergency fund to solve the financial crisis and keep investing in bitcoin consistently.
Anyone is free to do whatever they want with their cash but let's be honest, you can't be buying aggressively all the time it's not possible cause at some points you'll apportion your discretionary funds into other areas and slow down for a while, which makes lots of sense. I know it's the sacrifice investors who recently started are giving to build a better portfolio but then you can't sacrifice forever since you'll still need to go on vacations, entertain yourself and so forth one can only be aggressive for a few period of time, slow down then continue again after a while but saying that you can be aggressive althrough the year, for someone who recently started investing, I wonder the magic you want to perform, remember you're a human and having fun is part of our nature too.
I quite disagree that it's not a problem if you use all your discretionary funds to be accumulating Bitcoin because life happens and problems can unexpectedly arise. Ofcourse it's your money and you have a right to spend it anyhow you like but using all your discretionary funds to buy Bitcoin is not a good financial plan.
Inorder not to make financial mistakes from your total income you should first remove your basic or unavoidable expenses then the rest goes into your discretionary funds. You need to have a special budget for your discretionary fund, remove some money for emergency, Bitcoin accumulation, miscellaneous for your planned vacation, family treat or buying that gadget. The percentage that you decide to allocate should depend on their priority to you. The point is that your life shouldn't revolve around basic expenses and Bitcoin alone, although you can choose to allocate more percentage of your income into them, it's your money and your choice.