thats an interesting question that I think more and more are asking. Its def not the same for all total bottoms.
For myself (whom prefers to wear chastity during), I do not like to think my my own penis at all. It allows me to focus purely on my top and giving him pleasure which in turn, give me pleasure as cheesy as that sounds. Cumming during makes no difference to me, if I do cool, if not, cool. But as I do not tend to pay attention to my own, the instances in which I formally cum is few and far between. In most cases I experience full body orgasms or anal spasms with the occasional leakage out of my locked up penis.