I used to be a speedrun verifier for Portal a while ago and in general we'll reject anything that looks like very little effort was put in it. For Portal this would be runs somewhere above the hour mark, but obviously this varies for other speedrun communities which I can't speak for. For actual runs though it's common to watch them on 5x speed or faster as it's still relatively easy to catch someone breaking the rules at that speed. It also drastically speeds up the time it takes a run to get verified for such a popular game with a limited amount of volunteer verifiers.