Nebraska and Georgia... go fish ( The first is a Big Ten school ), Denver NFL is an example they canned John Fox because it wasn't good enough you among others last year were pitching a fit...guess what they made it the next step a year later.You are not going to see 9-3 college coaches get canned in 95% of circumstances. Maybe an SEC school who can stomach the big buyout but other than that no. Sure it's about the brand. Has been for last 10-15 years but coaches like Tomlin, Payton, Lewis keep their jobs. So do guys like McCoy. Obrien Gruden Garrett... The list goes on.
My point in the post was not only coaching but how many teams do not repeat. How many teams don't make multiple appearances in the SB. The NFL loves parity. Helps keep interest in the brand. How many times does changing a HC get you to the big dance? One that I can think of Gruden and even that's debate able Hell Payton was the golden boy free agent coaching target this off season but show me where his body of work is better than McCarthy or Tomlin. It's not. Perception is reality to many. Sadly so. Look how a bad change can set a franchise back or even a the college level. I get if you tank say 7-9 even 8-8 make a move.
I am NOT saying it's the way to go but sometimes coach's get stale and stuck in their ways and a change works, other times it fails. Your question was/is what is success..that like beauty is in the eye of the beholder.