I don't know why I'm hearing so much about 60/40 now. The recommendation that always made sense to me is based years-to-retirement. Once you get inside 15-20 years to retirement it makes sense to shift capital you'll depend on into safer places. To the extent that you've done well that tends toward a small percentage.

Allocations into Bitcoin have much more to do with education. People should get some, learn about it and buy more per the level of conviction they obtain. For the zealots, that's a Bitcoin standard. For the conservative, they may never get above 1-5% voluntarily but may find it growing with little reason to sell.