I was in a similar situation with former-Master - year long, long-distance, agreed that the distance couldn't be worked with. I was dating my now-boyfriend about five months later. I needed the time to decompress after such an intense relationship (D/s) and find myself again because of my sub role having me feel like a dog being abandoned on the side of the road. My boyfriend came along when I wasn't expecting to get with anyone.
If you feel ready, go ahead and date. There are no "required mourning periods".