If an item is still available, and the ad is reaching the end of the que and is about to be dropped off to the Archives, I see no problem with it being 'bumped'. It keeps the listing active and stops it being withdrawn from sale on the site. Makes the seller responsible for maintaining their ad.
But if the ad is only half way down the first page, yes, I do see it as not the best practice.
I understand the need to clean out older ads. Some people just forget to delete their ad once the item has sold, others don't give a damn.
I for one do post ads for services I provide, free services and for a fee. I've made these postings with Mike's approval too. But I have my own standards too, and I for one don't like to be seen as 'pushing' stuff, and I don't make a practice of bumping my own ads for the heck of it. To my own detriment I've had some of these ads fall of the end of the tree into the archives,

. But when I do 'bump', it is because of an innovation I'm announcing, or because it is about to reach the very end of the que and fall off, but the service is still very much available.
To aggressively 'bump' is not good, I agree. To 'bump' thoughtfully is a different matter. The mods are aware of this too.