According to George Michie, many PPC account managers pay too much attention to testing and changing their ad copy. Often tinkering with ad copy can actually drag down Quality Scores, as Google
grades keyword and copy block combinations on the basis of whether they've worked before. If you have a relatively well-performing combo and change it in the hopes of making it even better, the change
will immediately lower the ad's position or bump up the CPC--and you lose the original Quality Score. Of course, if the new combo does perform better, then it was worth the slight dip, but Michie says
advertisers are stuck trying to recoup the loss more often than not.
In addition to Quality Score issues, constantly substituting ad copy can lead to "hanging offers," or past discounts and calls-to-action still being left in the mix as active ads. Michie also says that spending too much time with ad copy can force campaign managers to ignore other factors that could have an even greater impact on the bottom line, like seasonal changes and the overall bid strategy.