What we need to do to keep the mediocrity level at it's lowly norm is to change coaching staffs every 2 years and get a new GM every 6 years.
GMs build a team to fit a coaching staff's plan. If the O and D philosophies remain similar, perhaps you can hire a bum HC and dismiss him early. But it you're hiring a 3-4 defensive HC who likes cover two, then go to an offensive minded HC who likes a jitterbug toy, then toss him in the s hitter after 2-3 years, then hire another clown who has no NFL Head coaching experience but runs a 4-3, then replace him after a year with a jerk-on head case who thinks he's god's gift to the NFL...
The Bills' front office has been in a 2-3 year rebuilding process that restarts every 2-3 years. Right now the current FO de jour is jettisoning some decent players that were drafted for the LAST coaching squad that held residence in the revolving chambers of the coaching graveyard that is One Bills Drive.
Maybe they got it right this time with Opie and his tar-heel friends. Lord knows I hope so, but until the coaching merry-go-round comes to a standstill there won't be any long term success that I can foresee that returns The Bills to relevancy in the NFL.
Go Bills!