You may be as patient as anyone could be, and that's fine. You aren't alone.
That said, if we fall short of a bowl game next season (which would likely mean Frost would have 4 losing seasons in his 5 seasons of coaching), year four at NU will be make or break. Not everyone is going to be as patient as you hope. Especially if empty seats become more commonplace.
Personally, I don't feel five wins in season three should be acceptable. I'm not alone in this thought. There are plenty of coaches who become successful much more quickly -- with plenty of issues in the program they inherit -- than the idea of a non-winning season in year three -- and, a "MAYBE" in four and five, as you suggest. Coaches that need that long tend to find themselves looking for a new school to continue their coaching career.