Why would you value a listing posted on Jan 2 over one posted on Jan 1 when the the Jan 1 listing is generating 10x the interest and traffic as the one posted on Jan 2?
The goal of a classified ad section is not to "generate traffic" just for the sake of generating traffic. The goal is to provide a place where people can efficiently buy and sell items. How well that goal is met determines how much traffic the classifieds will generate.
Similarly, the goal of an ad is not to "generate interest." You can have all the activity you want on your classified thread (increased short-term traffic), but if nobody buys your item, it has failed. Repeating this failure will eventually reduce traffic in the long term.
Put another way, why should an ad that's written well, covers all details, includes photos and basically leaves the potential buyer with no questions be passed over by an ad that is so poorly written that the buyers have to ask many follow up questions, request pics, clarification, etc. that then need to be answered by the seller?
So, you're right, I do discount the effort involved in "keeping an ad fresh." That just seems like fancy wording for answering questions that I should have answered in my original ad post.