Thanks for all the replies. It is certainly food for thought. I am surprised by just how much the pure S&P 500 approach outperformed the others. I appreciate the backtest link, I had considered a small cap etf allocation, too, and am significantly reconsidering it after using testfol.io. I'm squeamish at this valuation, but don't have any high commitment alternatives other than putting some percentage in BRK.B.

I might just go with the Buffett advice of 90% a very low cost S&P fund and 10% in short term US bonds (VOO and one of SHV, SGOV, BSV? tbd). I'd considered it before asking here.

Along with the small cap etf (IJR,IRS) idea I was considering, I'd considered something more conservative like GLD or a TIPS etf. I still can't stomach cryptocurrency, though. It has not been a joyful process to re-evaluate some assumpitons of my longer term financial plans this year.