It depends?

Are you 75 and retired? Buy some in hopes of handing it down to your kids. How much depends on what you've got. But it's unlikely to make a major difference in the way you live your life.

Are you 20 and just starting to work/make real money? Save up enough fiat to live 1 month if you lose your job, then start hodling, but if it's me, I'm probably building up to 6 mo. fiat emergency fund while I DCA into BTC. Oh, and if you're in the US and your employer is matching money you put in a 401k, you're stupid not to take it. Free money is free money, even if it is fiat. And investments aren't going to go to 0, even if the fiat does.

In between, it depends where you are, what your work and living circumstances are like. I'm closer to the former than the latter, have kids I need to take care of, a mortgage to pay, and could seriously think about retiring from the fiat mines in 5-10 years. So I'm still putting a ton of my investing in fiat-based investments, but I'm putting a little bit every day (thanks Swan Bitcoin!) into BTC. For me, hyperbitcoinization is a "maybe" in my lifetime, but if I can hand a bitcoin or two to each of my kids, they're going to be way better off than if I handed them the fiat equivalent.