Austrobogulator: Nah, that sounds like a bad idea. There are some threads that are valid to revive (especially in game specific forums). Also, there's a bunch of classic threads that need to stay open, no matter how long it's been since they were last active - such as the "What is this game?" thread.
Perhaps locking old threads should only relate to things that are really out of date - eg. rumour threads about game announcements from years ago or giveaways that are loooong over.
Hm, maybe giveaway threads should be locked once they are over.
They can always unlock them if there's a genuine need. For every one thread where there's a genuine need to go back and post there's dozens that have no such need. The ratio is a bit better when it comes to threads that get necroed versus ones that have a legitimate need, but even there you're talking about a minority of the posts. The posts where there's a genuine need are much less likely to go a year or more without anybody posting in them at all.
Even just adding code to the software to warn people that it's a necro thread would be welcomed. I don't want to waste my time going into a thread that's dead because some wiseacre thought it was cool to post some trivial tripe at the end and drag people into an old post.
Really what we need is some actual moderation, things like this wouldn't be an issue if there would be moderation. We have 1 subforum to do basically everything, and a lot of people don't seem to care, even the slightest about keeping things neat.
phaolo: I think I agree, necroing is usually unneeded.
I would exclude game subforums and stickied threads, however.
P.S: fall insomnia thread.. ..LOL
Subfora are a different issue. Those probably need to be combined as they'll regularly go a year or more without any activity in them. But, presumably, they could set different rules for the other subfora. The main forum is where most of this sort of thing crops up.