If you want to talk straight ROI I can give some insight. With a decent mix of BTC, Eth, and alts I'm a somewhat typical case study:

Started buying crypto end of 2017 (XRP was my first), Dollar Cost Averaged (DCA) until the end of '18, then got busy with other facets of life (new job, rentals, home renovations, etc.) and sat out all of 2019-2020. Just held my bags as is and was down most all of 70-85% those 2 years.

Fast forward and my portfolio is dead even, almost to the dollar as of Jan 1st 2021. I've DCA'd some more since then, and currently sit around a 2.5x.

IF I would of continued to DCA during 2019-2020... I'd most certainly be sitting on 10-20x.

THAT... Is why my only advice for crypto investors is to DCA and plan for this to be a long term, incremental investment... Just like a 401(k).