I’d like to stress that point a bit.
I had a vasectomy about a year ago, and being the weirdo that I am, I figured I’d see how much sperm remained in my ejaculate (and for how long) after the procedure.
I waited maybe two or three days after the procedure, and then for the next three days, I’d collect three samples per day and take a look under my microscope. In the first four or five samples, the swimmers were swimming hard. Told my brother (who had been trying for a kid for a couple years, and had observed his own samples trying correlate diet and other factors to improved motility) about the straight laser beams I was seeing in the scope — he nearly had a fit when I described how long it took them to go from one side of the slide to the other under the given magnification.
It was the ninth sample when there were very few observable sperm, and what remained looked kinda drunk and unmotivated.
All of that to say: if you’re going to get a vasectomy, when your doctor tells you to abstain from condom-less/birthcontrol-less sex until you come back for a sperm count, take that seriously. It’s amazing how motile they are even when kinda old, and also amazing how many hang around downstream of the vas deferens after many ejaculations. And, while rare, sometimes the vas deferens do manage to reconnect.
And a bonus tip along these lines: testosterone replacement, even without hCG, is not a reliable form of birth control. I’m on (and was on) TRT, without hCG, and the concentration of sperm under the scope looked higher than any YouTube video I could find at the same magnification (meanwhile my bro is taking silly amounts of hCG and struggling). I hear a lot of people joke about TRT having the beneficial side effect of infertility, but that’s far from a certainty.