Penn State has the perfect formula. They can screw it up though. But their formula is as follows:
1) We ARE Penn State! They have the brand name and brand loyalty to pretty much rank them in every preseason top 15 (and mostly top 10) from here on out into perpetuity.
2) Play 3 weak OOC teams and once decent one, the worse you get is 3-1.
3) 1 out of every 5 years you catch lightening at a white out night and beat Ohio State.
4) You beat Michigan now 3 out of 4 years.
5) Most years you avoid Wisky as a crossover.
So that yields 10-2 regular seasons and because of the inflated preseason ranking, the name, you may not win the Big 10 and make the playoffs, (once in every 5 years you win the Big 10) but you get that Fiesta Bowl or equivalent bid pretty much most years.
It's a great formula. Because of this you recruit well, so it is sustainable. There is only two things that could really screw it up.
1) That you think as a program you are better than you really are and put unreasonable expectations and start firing coaches their first real bad season.
2) Michigan gets good again (and that's no guarantee as it has been awhile) and one of the underlings (Mich State, Maryland, Indiana, etc...) get good again and Iowa, Nebraska or Wisky has a top 10 team and they are on your schedule.
That leads to 8-4's. 8-4's eventually lead to some 6-6's. And so on.