That's what all the "experts" were saying about Brewster. Well, he managed to drive our program into the ground in 3.5 years.
I agree that in a perfect world, you give the coach 5 years. But that assumes that there are some minimum levels of performance. As others pointed out, the BT is only going to get tougher, so it's ludicrous to pick a set # of wins out of the air as some line the new coach has to cross.
Instead, I think there has to be some set expectations of what sorts of progress need to be made. Areas include recruiting (esp. in state), graduation rates and off-field behavior, and just seeing improvement year over year. We could bring in Urban Meyer and there's no way Minnesota wins more than 5 or 6 games next year. And that's rounding up.
But S-canning Brewster was the right thing to do, regardless of the "5 year rule". If we see the same pattern again of regression, lack of player development, etc, we should hesitate to hit the EJECT button. After Brewster, our administration should be able to recognize the pattern.