The "5 minute" limits were for ensuring engines would last a certain # of combat hrs, almost all of them could run very hot, and overboosted for long periods, but your fighter wing could not be pulling engines every other flight when you had a war to fight, and win.
There was a memo from RAF Fighter Command during the BoB about pilots abusing the wep limits, and causing grief for the maintenace schedules. Not that I can't understand it, your up there in real life with your butt on the line, not just some game.