I have beat this to death on here, but I'll say it again. The 15 year mark is tough on coaches. Dabo is at year 16.
Spurrier did 12 at UF, Phat Phil did 17 at UT, Mack Brown 17 at Tex.
As much as we hate to say it. Saban had issues around year 14/15. We didn't necessarily lose a lot of games, but we saw slipping. Our D wasn't as stout, penalties, etc. The game changes in cycles and it is hard to evolve and recreate yourself when it does this.