Punto - since the oil is there to cool and lubricate the engine (thus protecting it from wear) then you are still using beans and will wear out then engine earlier than if you didn't use the 5 min rating.
As to limits, I'm with gomer and eagle - if you have to exceed them to avoid crashing or to save life (in extremis not routine) then pull away, but don't plan to do it. If you do exceed a limit, then for God's sake own up to it, don't let pride get in the way of doing the right thing - it might cost someone else their life.