For Sale Ads now Close 30 days after last posting.

I am contemplating limiting the total amount of time for an ad to 30 days from the start. (instead of from the last post) Should I do this?

This is a tough call. There are lots of sellers that may find this inconvenient and quit listing (A loss to all looking for parts). It's easier to bump than repost. (An ongoing discussion). But 30 days from last post won't affect the parts that "are" still for sale, just the ones that are long forgotten.