Like so many others said, sometimes you feel it and sometimes you don't. That can depend on you or the guy you're sucking. If it's going fast and deep all the way to the end, you might not feel or taste a thing, or you might just feel changes to his dick as he's cumming, even if you don't feel spurts of cum actually shooting out and hitting your tongue or mouth or throat. But other guys cum in long, strong shots and you can really feel it.
I used to suck off a young guy who came lots, but it was in an oozing fashion. You could taste it, a whole mouthful of it, but rarely felt a thing. He didn't shake or make any noise or do anything else to let me know he was cumming. It was just the taste that let me know it was happening.
The longer I do this sort of thing, the less I care about the feeling or even the taste, just knowing he came even if it was a drop and down my throat so I didn't feel or taste a thing, is enough for me. Perhaps I've had too much cum, lol, but now I care more about getting him off regardless of whether I get the traditional "reward" in any traditional way.