Looking at some of you #'s it looks like we had pretty similar timelines. Together since '90. Married 13yrs. Two kids. She moved out April last year. Personally I started dating pretty quickly, but everyone has their own timelines. Wasn't interested (and wasn't ready for) anything serious and I was always honest and upfront with that information. For me it was all very positive. Met new people, had some fun and tried to figure out what I was really looking for.
I've been seriously dating a woman now for the last two months. I think it is more a function of the right person than the right length of time. Of course I wouldn't want to go straight from the marriage into a serious relationship, but I think I gave it enough time... about a 1 1/2 yrs from her moving out. Things are going very well and we are both focused on the importance of honesty and communication.