Does the ability to delete a thread "expire?"

Like the title says, does the ability to delete your own threads for a paying member expire after a time? I've deleted one of my for sale/wanted ads when it was no longer needed but the last two I've tried to do that with, it only let me lock them. They had been up for quite awhile, longer than the other one. Just curious if that's just the way it works or if it's operator error. Thanks!

Also, I wondered if it might be possible to move this whole subforum up a bit, maybe to under the classifieds/wanted sections? I know I didn't know this was way down here until about a year after I joined and I tend to forget about it even now. Just a thought.

I believe you lose the ability to edit/delete after a post/thread is one month old.