Having little time to play, i have done only a few times mp. My main mp period was with Birth of the federation. Now i am doing pbem for the first time with Armada 2526 (testing for expansion) which i enjoy and have always been looking for (for 4x space strategy game which is my favorite genre). Now, i don't see the problem with my personal life to do a turn every day or every 2 days as i will most likely play anyway or going on internet. Here are the reasons why i have done little mp and none pbem.
1. Before playing against a human, i want to know the game very well and be at least able to win on average on a regular basis. Here comes the time factor. With so many games, there's only a few games i really master (armada 2526 being one).
2. I want to rely on my human opponent. I prefer to play against someone who visits the forums on a regular basis as i would hate to see a game not being finished.
Cheers