It's hard for me to put a number to how long I can stand those situations because it depends on how well I relate to the group, and when I was working I was never expected to be in a group situation for very long. The worst meetings were those that were practically irrelevent to me, and I'd get more frustrated and bored as the thing progressed, dying to escape. There was always a risk that they'd announce I was to be saddled with some undesirable task, and as support was often poor, the meetings would give me some stress because I was half expecting that to happen. Judging by the noise some of the participants made when they got outside the room, those meetings were a strain on everybody. Other kinds of meeting were of more interest to me, though I rarely got very much out of them because they usually talked too fast for me to keep up.
But we mostly worked alone. One of the worst things was young-ish people who would start chattering away near my desk, which would play havoc with my concentration. I didn't know how to get them to shut up or go away and do it somewhere else (perhaps there was no way), so I wore closed-back headphones and played unobtrusive music through them to drown them out. When the headphones got too uncomfortable I'd just stop trying to focus and either go and do some practical work in another room, or just leave the workplace for a while. If it was near the end of the day I'd sometimes even go home. Luckily we weren't very tightly managed so if I downed tools for a while, nobody noticed. By the time those noisy groups were a serious issue, I'd been diagnosed, so I felt that if I were challenged then I was fairly safe.