Google places more weight on ads that have been running on a longer amount of time because Google trusts those ads more and has a better under standing of how the ad will perform. Therefore, in highly competitive verticals the age of your ad becomes almost as important as the account structure.

It’s important to constantly test your ads, but what’s the best way to do so? In my experience it’s best to test ads a few ad groups at a time instead of, say 80% of your ad groups. If you add too many new ads at once, Google can penalize your ad groups with lower positions.

I agree if you run your new ads long enough they can become Foundation ads, but how long does it take before that happens? In my experience it takes between 5,000 to 10,000 impressions.

Quality Score exists (in the Google algorithms despite how it is reported to us) for keyword-TextAd pairs. When a new text-ad is created in an ad-group, QS has to be determined for the resulting new KW-AD pair. Google does this using the factors they’ve described. There will be some assumption about the new ad copy until it proves itself (details unknown, but we can assume an overweighting of other factors). Google has made clear that they do not want to penalize testing and incremental copy improvements.

The idea of ‘Foundational’ or long-running ads suggests that their longevity is a beneficial factor. I don’t believe this is true. If they have a better CTR, or perhaps better relevancy, than your promotional copy, helps your averages during the test, and the history will help the ‘benefit of the doubt’ your new ads get. If they aren’t better (particular at CTR) than the ads in test, they won’t help at all.

Also, once any new ad copy has established an equal CTR with a substantial number of clicks, it could be considered ‘foundational’ in that it will have just a good a quality score as even a much older ad.

And assuming you’re using the ‘rotate’ ad feature, much of what the ‘foundational’ ads is doing is simply limiting the size of your test – which is good and safe and prudent. But once you see a great CTR for a meaningful number of clicks, don’t be afraid to let the new promo ads run alone – QS will not suffer (meaning you could temporarily pause the ‘foundational’ ads).

Plus (there is much detail to fit into a comment) dont’ forget that ‘rotate’ doesn’t really rotate evenly because the higher QS of certain high CTR text ads will make them eligible for more auctions, so they’ll get overweighted no matter what you try to do.

In the end, quality ad copy that drives good CTR earns high quality scores. Having something you know works is great, because many tests won’t. Keeping known good ads in the mix during testing is smart too. But I don’t believe anything Google has ever said officially (or under the table) about Quality Score suggests that keeping core ads a long time helps. The post didn’t say that specifically, but seemed to suggest it, so I wanted to clarify that point.

All of the above limited to the best of my knowledge. I only read the tea-leaves like everybody else (but I read them carefully .

Another great post about PPC ads by you. Love it.

One quick thing to mention about foundation ads. If your campaign is set to optimize your ads (show better ads more often), some of these foundation ads may have a lower “impression rate”. Your call to actions ads may outperform. However, that’s okay because these ads are in the account to serve a stability function.

Once again, good stuff.

Cheers!

Peter