I'm trying to get back into it and do around 4 x 18-20 hours fasts per week. That's what works best for me and my schedule, and I'm used to those kinds of fasts.

I think it's more beneficial to do more often and short fasts (i.e. 16, 18 or 20 hours) than to do one long (i.e. 36 or 48 hours) a week.

Just my 2 sats