Buying dogs specifically for breeding

I put any dog I'm thinking of breeding to the test to see if they are what I want to produce my next litter out of. But after I know that the gyp is what I'm looking for she normally goes up. That way she can't get hurt and I can get more dogs off of her when I need to. That's why sometimes you hear me call certain dogs off my yard brood gyps. For those that have seen the tests they are put through they can tell you that I expect a lot more out of a brood gyp than I do out of the dogs I work. That's my way of insuring that I try to pass on the best traits for me and the breed in the next generation..Just my two cents worth... I figured you would have had more answers on this thread..