For Sale Ads now Close 30 days after last posting.

Craigslist ads have an expiration...but the posts disappear entirely whether or not it sells.

The whole point here is to keep ads from being posted in when the owner isn't here or the owner forgot to mark the ad as sold. When someone posts in a thread, then its brought to the top of the list. So an ad from 2013 for example, could be top on the list again.
If this IS the whole point, then 30 days is too aggressive to eliminate a 3 year old post from returning.
Active sellers will create additional threads to sell the same part, effectively INCREASING the number of For Sale ads that appear as New Posts!

Effectively making more 'open' threads, just not on the front page. Same with people opening a new thread instead of bumping it. The original thread is still there and looks like it never sold.
I agree with the point that @zkx14 made here...If I'm creating additional threads every 30 days to advertise the same part, when the part finally sells, there are multiple threads to be marked as sold.

Perhaps there is a better interval to use that would solve the problem described, without increasing the efforts to sell a used part...

Thanks for reading,
burg