The upside of remaining focused on a task such as sucking Watson's cock, while Watson returns the favor, is that Holmes is sufficiently distracted to be able to prolong is his own stamina. That's important when coming out of a dry spell, which usually leaves Holmes feeling ready to come apart under Watson's touch. He holds himself together as long as he can until finally Watson's mouth is simply too much.

He regrets it, but he releases Watson to press his face against Watson's thigh, hissing out a warning before his muscles start to tense. He gives a small, quiet cry when his orgasm hits him, and remains still while it reverberates through him.

When he recovers enough, he lifts his head and resumes his attention to Watson, eager to help him to his end, knowing that he can soon collapse into Watson's arms.