As Pegula I think I would give my coach 3 full seasons to make the playoffs . They get one year extra on their contract for making the playoffs, two years for winning a playoff game, 3 years for making the Super Bowl and 5 years for winning one.
To to your point OP. McDermott has things to learn and I believe he will. He seems willing to learn and adapt. He also seems to have the right relationship with the GM.