For my two cents, I really don't see any difference in motion, flex or triangle in the engine, so I would see zero purpose in running multiple offensive sets. The only benefit to doing so that I can see would be if there was evidence that a particular offensive set fared better against a specific defense, allowing you to change and gain an advantage.
But I've been here since '09 and I don't remember ever hearing someone theorize something along the lines of "flex is better against man" or "motion is better against the press" than other offensive sets.
I could see maybe a token argument to devoting some minutes to fast break, just to have it available as an option to shift into if you're trailing late in a game, but on balance I think the minutes are better served in individual development and getting players to their caps in the core categories faster.