It depends on the situation. Many's the time when both guys understand it's a "blow and go" - I blow, he goes. Unless he wants to get me off as well that's how it's left.
Then there are other times when the other guy's energy level is higher. In other words, his high fitness level or relative lack of years means he can reload and be ready for another round in short order. That's when I chill after the first round instead of nut, then join in climaxing at the end of Round 2.
What gets ME steamed is when you rock your skills on somebody for some time (in some cases over two hours) only to have him then say, "I don't wanna cum right now."