Once you accept that there's no bigger (or other) star in the WWE than Roman Reigns, it makes sense that there's no reason to take the belt off him for a very, very long time.
I suggest they go all in on that, and have him still holding it heading in to Wrestlemania 40 when he'll have been champ for 3+ years, and could build to an absolutely massive main event for a landmark show against one of the new NXT guys who god willing should be ready to be a star by then.
What do you think sirs?
Oo! Oo! Like Dexter Lumis!