Sure, if I was researching how to spend my money and an ad responded to my need.
Repeat visitors can be great prospects for advertisers (or for affiliate sales), at least for certain topics. But don't take my word for it--see DoubleClick's "Research Before the Purchase" study, which was published last year. The study showed that most online purchasers don't buy during their initial searches; they research purchases multiple times over a period of weeks or months before making a decision.
Getting back to the topic of this thread, CTR can be affected by a lot of things, including things beyond the publisher's control such as where traffic is coming from. Hypothetical example: I have a European travel site, and people who are researching travel purchases are likely to click and to convert for advertisers. But if my site were suddenly to be featured on a directory site for K-12 geography teachers, I might start getting a lot of traffic from schoolkids researching school reports, and both CTR and conversions would go down.