How Long Before A Game "Overstays Its Welcome"?

[firebush03]

My limit isn't necessarily in the number of hours I invest into a game; rather, how many weeks it takes for me to fully beat it. For instance, if I purchased a game in mid-July and I'm still playing it in mid-September, unless we're talking about Zelda, Pikmin, Mario, or some other major Nintendo release, I'm moving on to something new.

What about you?