With all the games being published nowadays and people buying them it seems more often than not we are playing the "new game game" over and over again, just learning new game rules and playing a game once or twice then on to another one.
This is what killed my enjoyment of the euro-gaming group I used to host. We'd play something new every damned week and almost never go back and replay anything. It frustrated my wife the most, who basically dropped out of the group once we added another person to cover for her. Eventually it burned me out as well and that along with some of the stupid internal bickering between members led me to give up my hosting duties once and for all.
With wargaming it hasn't been as much of an issue as I tend to spend the majority of my time with certain systems. This summer, for example, I've been going on a
La Bataille run, which has been nothing short of awesome. It's amazing the little nuances and such that emerge from a ruleset when you spend a lot of time on it. I could probably prune my wargame collection down to four or five systems and be a happy man (of course making that initial decision on which four of five to stick with might be a little tough).