I play casual and competitive rounds with a Fade Crunch so I have to play kinda light. For most rounds I only throw 4 or 5 discs as they end up getting that special feeling and I lose confidence in my other discs unless I get into a shot that I've performed dozens of times on my home course.
On my home course I only use 5 or 6 discs for any round. After playing the same course hundreds of times, I know the lines I'm going to throw (save for trees hit and sloppy shots) and how to get out of areas I need to get out of, so there isn't a need to bring along my whole bag.
Discs on hand: 3 putters, 3 mids, 9 drivers. Most everything is understable with only 2 stable discs in the whole bag for when I know I need stability.