I think there is something to be said about Head Coach consistency. If you look at the 2015 NFL play off bracket you had Colts, Bengals, Ravens, Steelers, Broncos, seahawks, Packers, Cardinals, Panthers, Lions, Cowboys.
Bengals, Ravens,Patriots, and Packers have had their coaches for a while. Cowboys and seahawks have had their coaches for around 5 years I believe. Drawing from memory on this.