I've never used frozen semen, and I've never had any of my dogs frozen. That being said, there have been plenty of dogs frozen that weren't the best of the line. I can think of a few dogs off hand that were frozen before they were taken out, only to win/lose and pass on afterwards. I do know of someone who uses frozen semen from his passed on stud, and he's had winners out of each breeding he's used the semen.