I don't know how long I'll play. Probably until something even better comes along.
I bought Killzone 3 not too long after launch, and jumped into the MP being pretty good off-the-bat (after just a couple levels of the campaign to understand the game mechanics), but put the game down for almost a year. I decided to pop it in about a month ago, assuming I would probably suck **bleep** no, and to my surprise I was still very good. It took me a round or 2 to get the controls down again, but I'm probably better then I was last year. Now I usually have at least 2x as many kills as deaths (My best match so far was 29:9:5).
Hopefully if I decide to stop playing All-Stars and get back into it later, I'll have similar luck and not go 3:17 every single match after taking a hiatus