"worst in my opinion is buying embryos that are "sitting in the tank" and have been there a while ... probably some already got put in and weren't so great... therefor the rest are still "in the tank"... it really takes some fortitude to destroy embryos whose flushmates didn't hit the mark although I think is the smart thing to do..."
I respectfully disagree with your opinion that embryos "sitting in the tank" were from matings that weren't so great. I would say that 95% of the embryos in our tank worked well. I can only remember 1 or 2 matings ever that I wasn't please with most of the calves. In those instances, i liked the bulls, but not the heifers.
In a constantly changing industry, we are flushing to new bulls annually. In an effort to get in the newest (and what we think are the best) matings, many of the good, old matings remain in the tank. Not because they are matings that didn't work, just because the new matings take priority.
I assume that many breeders are in this exact same situation.