On ICCF the time control is 10 moves in 50 days. I like this as you can play as fast or as slow as you like. The time accumulates. For example in one game I have 132 days to make three moves (move 40, the next time control). My opponent has 186 days! The last game I played here was fairly fast, I think we wrapped it up in a week.
I don't really like 'fast' correspondence games obviously. As far as game load I have 13 of 16 games active in two tournaments with another 10 game double rr starting on the 1st. 23 active games would probably be too many except four of my active games are pretty much wrapped up. For me 20 is probably the limit.