A few comments from someone with not enough cows to have any credibility.
First, weaning a 710 pound calf does not impress me unless I know how much the cow ate to do it. Big calves out of small cows is better, though size is not perfectly correlated with feed intake.
Seems to be alot of gamblers on the board. And most gamblers I've known aren't very good at math and the laws of probability. They seem to remember the times they won more than the times they lost.
If she has a 50% chance of having the same thing happen, then you need to figure in that cost of keeping her.
I understood that serious producers look for reasons to cull, not excuses to keep cows. If you keep finding excuses, you will often be wrong, and the cow was the problem, and will have that problem again, or pass it on to offspring. If you keep excusing problems, you end up with more of them.
And of course, buying cows at the salebarn, you have to wonder why a younger cow is there. Perhaps someone took the advice given here and sold their problem to the next sucker.
I have a brother who wanted to buy open cows at the barn and rebreed them for fall calving and sell those that didn't take. His vet said it sounded good. I suggested that first, he would immediately be selecting for infertility. Second, if there isn't much profit in cows to begin with, seems there would be even less with cows you're feeding without getting a calf.
Which is funny because he's very against gambling at casinos, but fine with it otherwise.