I have to agree with the "no problems with it" folks.
I understand that often the OP has their answer, no longer cares, or has gone inactive by the time someone ressurects a post, but if there was an expiration date, I would think that the staff would go through and lock or delete old threads. If the staff hasn't locked it, it seems to me that it doesn't hurt anything for new posts to be added.
I found this forum through internet searches when I NEEDED information, and while I'm computer/internet savy enough to check how old a thread is, maybe my neighbor is not so techno-oriented. And if someone needs a clarification on some good info that was posted last year, I'd rather they ask in an old thread than go without the info because they are nervous about starting a new thread when they don't really know how to navigate a forum or which section to post in.
I personally resurrected an old thread with a link to a good website that tells how long stuff stays good to eat. Admittedly, I resurrected that thread without realizing how old it was. (I just didn't look). But the info is still valid and valuable, and others were soon posting in there as well, so clearly I wasn't the only one who wanted to know how long my fresh eggs would be edible if refridgerated.