This stat is kind of flawed. It's not like they had 3 guys who did 25, 15 and 20 years. JoePedo made up the majority of those years and no one was going to fire him until... well. I don't like the logic that just because they kept one guy for for 45 years doesn't mean they won't all of a sudden make rash decisions. I mean they fired Franklin mid season, who's previous three seasaons were 11-2, 10-3 and 10-3 (with a CFP appearance).
I'd say the odds are that Campbell will be dealing with an AD/fan base/donor issue that's a lot closer to Franklin's tenure than Paterno's. I'd say Pedo State is definitely a lot closer to "Win Now or be gone." program than a "Let's Keep the guy 40 years." program. Hell, Franklin got the benifit of a few growing pains just for the aftermath of the Pedo scandal. I don't think they will can him for not winning an NC, but they aren't going to keep Campbell around if he's not solidly in the play-off picture most years.
I think CMC's biggest issues are going to be his game day decisisions, clock management, etc. (Sorry, I never thought CMC was a good game day coach.), his lack of emphasis on good special teams and those "In the margins" things that seemed to cost us games. Unless things drastically change, CMC is always good for at least one or two headscratcher games a year. (See Colorado this year.)