4-6 minutes until "brain death" sounds like blood chokes wouldn't be dangerous at first. However brain death is the worst case scenario and in the minutes leading up to it, parts of the brain are dying.
Blood chokes are serious shit. No they don't add up, and getting choked for 10 seconds won't permanently damage you. However, getting choked for 30 seconds will. I remember a match in the early days of MMA where a rear naked choke was held for about 30 seconds until the towel was finally thrown in; when the choke was released the guy immediately went into a seizure and was unconscious for several minutes. I remember a news article ffrom last year where a kid was showing off a rear naked choke at aa party, held it for around 30 seconds, and inadvertently killed his friend.
Choking is bad for you. It seems like a lot of people in this thread somehow forgot that strangulation kills people and puts them in comas; and no, it doesn't always take 4 to 6 minutes. Depriving oxygen from your brain will cause it to shut down, and the longer the brain is starved for oxygen, the more of it will die. I hope nobody honestly thinks you can hold a tight choke for a full minute without putting the person you're choking in serious danger of brain damage, becoming a vegetable, or death.