Dad (and the NRA) taught us to wait at least 30 seconds. Obviously this would not apply to a defensive situation, or combat, but sport shooting, hunting, etc. its good advice.
Hang fires used to be more common than they are today, but they still happen. Today there is a much, much higher percentage of complete duds over hangfires, but it can still happen.
Most hangfires do go off within a few seconds, but some take much longer, and while a full minute is extrememly rare, its not totally unheard of.
I don't shoot competition, but isn't ammo malfunction (dud, hangfire, etc) the whole reason there were alibi rounds? Or do they even do that anymore?