Several times but most memorable was a few years ago at a house party with an ex, the party was on a decent piece of property about 5 acres so bunch of people set up tents out back, we set ours and the Ex's BFF set hers up literally right next to ours. The BFF and one of my buddy's were single and seemingly into each other so we worked on hooking them up, later that night me and my ex head to our tent, she got insanely horny when she mixed weed and booze, we're going at it when we hear my friend and the BFF return to her tent, my ex is giving me head when they start getting to it, we hear him say he doesn't have a condom and she tells him to just pull out, so they start to fuck and he lasted maybe 2 mins, i knew from my ex she hadn't been laid in months so she was still gung ho to get some they fooled around a bit more but from the sounds of it he was a one and done minute man, he left to go get a drink and that was that. Me and my ex were able to go for well over and hour at that point in our relationship and we did just that, we'd been going at it for quite a while when we started hearing noises and realized her BFF was masturbating to the sounds of us fucking, something she admitted to later, after that night the BFF always joked about sharing me if the ex ever needed a breather. One thing led to another and one night my ex agreed and we had a threesome