No, my DH hasn't had this done, but I studied this at Uni and have had some SA results back at work so I know a lot more of the theory than the practice.

I would trust the test that was done the soonest after the sample was taken, and you should always be asked for two samples to be tested at the same lab anyway. However, if you're trying for gender swaying a girl, onlying bding 3-4 days before you actually O, then it would be worth taking the results of the test that was sent away.