Guys how many time i mean how many days require to see that the earning of a ad unit when we change its location or colors etc thanks in advance for your suggestion.
The change takes affect almost immediately. I assume next day you should see the difference, of course if number of visits to that page was the same and not 0. It is up to you to decide how long to wait,, d\a day, a week or month. The longer you wait the more accurate results will be, as per big numbers law.
Depends on your traffic. If you want to do A/B testing, maybe a week for each implementation would be fine. It depends on your number of ad impressions in fact, you need thousands.