A couple of years ago I was in the US on business, travelling with a younger (29), super good-looking, male work colleague and we were sharing a room. Keeping it professional we were, of course, in separate beds!
On the second night, I woke up in the middle of the night to hear him mid 'dangerous wank'. The sound of his muffled breathing and slow stroking of his cock was more than I could bear and so, without him knowing (I hope), I joined him stroke for stroke before, judging from his stifled sigh, we both came at the same time.
I guess we must have just both fallen asleep, but in the morning, while he was down at breakfast, I found his cum-stained briefs tucked under his bed where he'd cleaned up from his nocturnal emission. The cum was still damp from the night before and so I put them in my mouth, shot my load alongside his and, now wet with my fresh morning load, put them back where I'd found them.
Plenty more stories just like that...!