What happens to old threads on here
 

Do they fall off the edge after a while. I check back now and then, but some just disappear.

Archive'd!

Check out the "archive" link at the bottom of the screen.

Semi-ontopic: What exactly is the rule on gravedigging here? I've noticed that far more than everywhere else threads here seem to get resurrected periodically sometimes from years of inactivity.

The search feature is another good way of digging up old threads.

There's no rules against picking up on old threads. It's pretty fun... often shows the evolution of thought for a given member when they respond again.
We used to request that people search and see if they can find something on their topic before starting a thread, but that trend is no more. Sometimes the old applicable threads are mentioned or linked in the new ones, but not always. I try not to link them too frequently, since it tends to slow discussion.

I seem to recall that the rules used to be you were obligated to seek out old threads and bump them with your new input to prevent 30 threads about the same topic. One problematic example I can think of: threads about evolution.

Sometime after, during one of TFP's drama filled identity crises, it was decided we weren't going to enforce that rule any more and that multiple threads addressing the same subject was No Big Deal as long as they weren't active at the same time.

We only show "active" threads, with "active" meaning a post within the last 30 days. You can change that default setting at the bottom of a page, though.

There isn't a rule.

I was one of the ones that killed that rule. Not much pisses me off more than seeing someone new coming to ask a good question in their first post and seeing a bunch of "search feature noob" posts. TFP is supposed to be welcoming, so we eliminated the opportunity for petty displays of superiority. Full blown displays of superiority are, of course, still just fine.

At this point, we encourage folks to use the search feature, but if they don't, it's no big deal. If there's a thread that already covers the topic, we might merge the two, which would bump the old one back to the front. Or we may leave it alone if there's a new angle on an old topic. Personally, I've found that it's always better to start afresh with a difficult topic (abortion, immigration, homosexuality, etc.) where minds are generally already made up.