Occasionally I'll go back into a multiplayer game I've been enjoying and find that an experience that had been smooth, effortless and fun is now clunky and unsatisfying. When I get that feeling I know my time with the game is over. I may try to play it a few times in the future but I won't get back into it. In most cases I'm fine with this. I've had a great time and there are other games to move onto but sometimes things don't work out so smoothly.
Luckily, I've never had a games multiplayer servers shut down on me or had a game changed in a way that I could no longer play it but I have dropped out of playing a game early in it's life (Phantasy Star Online) and then, with the Dreamcast gone, had a crazy nostalgia for the game and a desire to go back in but no way to do it (I think it was on PC but I've always been on Macs.) I've also lost interest in a game that I absolutely loved for years and stopped playing, wondering later, if I'd just made a bit more effort, I could have carried on playing and having fun.
There are also those rare games that you leave behind for the good of your job/life. WoW fell into that category for me just because I lacked the will power to play it in moderation. Self control wise I'm all or nothing. With WoW it had to be nothing. Although, if I'm honest, I have occasionally popped back in on a ten day trial just to be in that world again for a while. I have no desire to play it full time. Thankfully.
What are your experiences?