Those who experiment with their placements to bring high CTR - how many days do you normally wait to test your CTR? Lets say you launch a certain template today - you wait a week to see and analyze your CTR - and then change the template (adsense placement) ? (Assume you are getting traffic from G!)
A week is probably a reasonable time to assess your placement. You certainly don't want to wait less than a week because some days of the week are naturally better than others.