I do not really think that is a very great issue. Sperm usually is not long lived as far as i know.
But another thing that come´s to mind is that not also 2 pairs would have to spawn so close to eachoter in time changes are very low and of course eggs are so quickly fertilized after the female releases them also the cange that the current leads it to the right place in the right time…
I think the changes would be very slim indeed.