Do you guys think it's a good idea to change ad layouts on a fairly regular basis? It seems like it would be a good idea, especially if you have a lot of repeat visitors who may start to ignore a constant ad location.

It depends I guess. If you get a lot of search engine traffic I don't think it will help. IMO there are just spots on your forum that bring in a good CTR no matter what. If you have good SE traffic these are new visitors and you want your ads in the spot where the CTR is the highest.

For me, it'd be a members only thing. I display different ad layouts to guests. Members just get a leaderboard under the navbar.

I recently changed the member's advertisements to a link unit to deter any "click attacks". I don't think many people realize that if they click your ads too many times your account can be banned.