Dunno man, I hadn't given that much thought to my workout's duration, because it had never occurred to me that there is a minimum amount of time training should last, so I never trained with a watch around my wrist. But still, I think the guy who said he can do it in 5 minutes was exaggerating
I've never considered a minimum either, but I can say that the list at the start of this thread wouldn't be much of a workout for me - and it's personal effect that's the important thing.
I could go through it in (as the saying goes) 5 minutes (it'd honestly be between 5 and 10) - but I know plenty of people who couldn't make it to the end...