I think you should play exactly 4 games at the same time. No more, no less. Anyone who does otherwise proceeds at their own peril.
About correspondence chess

Thanks chrisr2212,
I also started to feel like I've been playing too many games lately so I might as well drop to 10

Hi Daeru,
depend by your aims.
If you want play correspondence chess games to improve your calculation and your knowledge about chess , you must play few games at the same time.
I tip you to play 10 games - max 15 at the same time. Because is better play few games with commitment then many with neglect.

That's still too much!
Take my word for it, 4 is the perfect number.
that because you are playing 4 games atm.

1543 games at once
3 days a move 3x24 = 72hr
6 hours sleep a day 72-(6x3) = 54hr
1hr a day to eat, toilet, shower etc. 54 - 3 = 51
51hr = 3060 minutes
split between 1543 games leaves 1.98 minutes per move.
if you dont go to the toilet you might get it up to 2min/move.
do you have a job?

http://www.chess.com/echess/profile/bjonil60 this man does it!
How many games do you think one should play simultaneously? Some play 100+ games at the same time while some play 1 game at a time.