I'm torn on this one. I can see how you'd feel that he stole your hard earned rewards that you'd been collecting. You did say that he had been in and out of the room several times, so it's not like he just walked in and slurped your loads out. On the other hand, you're in the sling, which means your ass is available for anyone to use. He just wanted to use it with his tongue instead of fingers, toys or cock. I can see both. I'd probably initially feel the way you did, but I think I'd feel complimented that he wanted to slurp direct from my chute after watching me take cock after cock. Honestly, I've been all 3 parties in this scenario before, but I generally ask the bottom if I can taste his cummy hole before diving in -- unless I've just cum in him, then it's still mine until I walk away. if it's my hole, I enjoy a tongue in between fucks, but it ALWAYS makes me want more cock!