The reality is that this game can get monotonous after a while.  A co-op can give rewards and really adds another dimension to the game.  There are co-ops just for loyalty points, some that just let life happen, those that have a relaxed structure to compete but not interfere with life and those that are ultra competitive.  Some are silent and some are chatty.

The key thing is finding one that fits you.  It is time to leave a co-op when you don't enjoy it anymore.  If your leader makes you feel like a number when you want to feel like a person, or nobody does projects and you want to, it is time to move on.  I ask that when you leave, you let the leader know why.