To me, it wasn't more than a day or two. But at first it's awful, a few times I just forgot to upload a custom thumnail, and couldn't change it right away. The nerve.
Ahh not so bad then. I think I'll just remain patient, it's just the paranoia that gets me! I like to know that it actually has worked and that I'm not wasting my time waiting for something that's not going to happen!! haha