Natalie was conceived on our 5th cycle TTC. (Though one of those DH and I were cross with each other around O time, so I don't think that cycle counts as such because we weren't BDing.)
Haven't started TTC #2 yet, so can't help with your other q's. Though my brother was conceived fairly quickly, then my sister took my parents 5 years and I was another 4 years after that... So subsequent babies aren't always quickly conceived.