With my DS is was 10 months of no contraception but not actively "trying" - plus 10 months of conciously tracking "O" and trying hard (so 20 months to answer your question) DH was finally discovered to have some semen issues and we concieved after 3 months of menevit and chinese herbal teas. With this bubba it was 2 months we were a bit surprised! We definitely expected it to take longer!