Bitcoin Power Law is the simplest of the long term trend models, and imo is quite beautiful.

https://onebig.life/powerlaw

https://m.primal.net/JCEp.png 

I've just built this page showing the beautiful straight log-log regression line, with a price/date calculator. No trackers and no VPN blockers (I'm talking to you, Bitbo charts). Just a free service from one bitcoiner to others.