Indeed - it's always said "A minimum of .... minutes" and a few games I've seen recently went well beyond the stated number for the reason you state. I think the Liverpool v Man City game went a few minutes beyond what had been said.
if the ref played under five - no idea, I was at the game -...
I'm not sure it's the easiest part of their job in the context of everything else going on in a Premier League game, but I certainly think it's the bit of the job there's least requirement for them to do.
David Dein was on a recent Football Ramble special and he said that all referees he has...