Madadder's right. Autolocking old threads would lead to even more repeat threads than there are already (if such a thing is even mathematically possible). I'd much rather see old threads revived with new content than see twenty threads on the same subject; the same arguments inevitably get hauled out all over again anyway, so why force people to continually repeat themselves?

You can't make any suppositions about whether posters stopped playing the game, really, especially considering how many posters are clearly in for the long haul. More importantly, whether or not the OP - or indeed anyone else posting in the thread - is still playing is practically irrelevant. A good idea is a good idea, whether or not the originator is still active within the game. Obviously patches that address suggestions are the exception, but what would anyone be doing reviving a thread making a suggestion that's already been addressed anyway?

I would like to see an end to resurrecting old threads in order to disagree with them, as letting bad ideas die off on their own is a pretty useful and largely self-regulating signal:noise filter. But that's less common, and anyway an entirely unenforceable regulation.