Also other q - sperm start to replenish immediately - he's always making more all the time. There's never a point where he's not making them. But it's not like a gas tank, he's never "empty" or "full", he can have 20 mil, 100 mil, 400 mil in a single ejaculate and (all of them are normal amounts) and then there will be more living sperm, in the next batch even if it's right away.