I only used my OPK's for one month (cycle) and it was negative until one day it was positive with two dark lines. That month we were successful and bump is due in January 09. So that's the only experience I can speak of. I have a pack of 10 sitting in my top draw that I haven't even opened yet as I thought for sure it wasn't going to happen the first time we tried. I am glad I was wrong, I guess I will just save them for next time.