I have a set of ads associated with each of my keyword groups. Since the best-performing ads will always be the ones that show, is there harm to my quality score if the "bad" ads stay in the mix? Should I trim away under-performing or less-relevant ads even if they aren't showing, and is replacing better than just adding better quality ads to the set? I'm really struggling with relevance even though I've added a variety of directly relevant ads to the mixture.
You can leave the ads or keep pausing and adding new ones until you end up with a better performing ad compared to your current best... either way. Your quality score is not harmed by leaving them... but if none of your ads are performing well, your quality will, at some point, be affected. If your account is fairly new, it is expected that it takes time to dial in an account.
We prefer to have 3 ads per ad group. When there are under performing ads, we pause them (never delete or edit or you lose the history of the ads) and create new ones. You can copy & paste ads from one group to another (or from the same group) and then edit the copied ad for ease of use.
Keep your ad groups tightly defined with a low amount of keywords (1-15) and give each group three ads that use the keywords and terms & topics from the ad's landing page. It takes roughly 30 days of history to truly understand how things are going.
Please review this information about ad rotation and frequency capping, which also affects your ad usage.
All the Best,
Google AdWords Top Contributor | Google Partner | GYBO | Local Guide | My Profile