I do various versions - Dr. Jason Fung says to do what works for you.

Dr. Fung does the one meal a day version (aka OMAD, if you've ever seen that acronym).

I USED to be able to fast for days at a time; I've done several days in a row. However, since I've started the lithium, I am having a really hard time with it.

Now I'm lucky if I can get it down to a four-hour eating window.