When are old adds removed?

I have replied to several ads listed for rent (at least 7) and all but 1 have responded that their unit has been rented, yet they are still showing as available several days later. How long until they are listed as rented as I feel I am wasting my time..

It's up to the owner of each ad to remove it or mark it as "Rented" or "sold".

I believe rental ads are for 6 months and for sale ads are for 12. So if they aren't removed as sold or rented by the owner, they will expire and be removed on the schedule above unless the owner pays to extend/renew.

See the response to you other question about getting your membership fee refunded if you can't find anything suitable in the first 30 days.