I personally think that those who invest in Bitcoin should take sound and reliable decisions for their investment.
Of course, every investment has a risk, even if you are ready with all the risks you take. That's why we have to use reserve money in investing because we know it's cold money that we won't touch in the long run.
Everybody has their own strategy but in this context I think when you use your spare money, isn't it a deterrent for unexpected needs?
I personally prefer when budgeting every monthly income to be used as investment money. Because in my opinion when using spare money then this possibility can slightly hamper when there are urgent needs but when budgeted in advance to invest, for example like 10 percent every month then apart from you can know how much your capital is to invest, you can also use your spare money for other purposes such as unexpected needs or prepare to face some chaos such as inflation etc.