I guess I need to clarify...
Perhaps it'd be easier if I discuss in terms of disc selection vs. type of shot. On a par 54 course, you should be reaching for a driver (Distance, Fairway, Midrange) at MAXIMUM 18 times. If you shoot a 54, you will therefore reach for a Putt / Approach disc a MINIMUM 36 times.
Understand that while these numbers will fluxtuate... based on course and performance... an average round should always have a sizeable difference in use between Drivers and Putt / Approach. The irony here being most players obsess over carrying tons of drivers... and one putt / approach disc (which they commonly refer to as their "putter"). It should be reversed. Your most variety of molds should be in your Putt / Approach and Midrange Driver categories, followed by Fairway Drivers, and finally Distance Drivers.
I rarely throw a driver (Distance, Fairway, Midrange) 18 times on a course. It'd have to be a pretty long course. I'm reaching for a putt / approach disc whenever possible. I follow that with my Midrange. Fairway drivers when I have to. And Distance Drivers only when I can't reach with anything else.