You CAN edit and delete posts, but not for an indefinite time period. I don't think it would be a good idea to allow deletions forever. It would mess up the whole flow of the board. A lot of the posts are debates about important local issues. It would mess up the whole flow of discussion if posts just disappeared. I don't know if there is any way that a different deletion policy could be applied to FOR SALE threads. I kinda doubt it. If you really want to know if something is still up for sale, send a private message to the person who made the offer and ask.