My rule of thumb. If I got the invitation because the baalei simcha want me there (my siblings, close freinds) then I will stay until after sheva brachos. If I got the invitation because the baalei simcha feel they must invite me out of some social obligation, such as a (not so close) neighbor, some guy in shul who believes my name is good shabbos, a co-worker or I’m invited because I’m the other half of the mr and mrs, they I go for the chuppa, dance a little with the baal simcha and leave. He was yotze and I was yotze. Such a pathetic way to look at things, but its what works best for me.