I'm curious to how many flies most people carry. Also, it would help if you provide some idea where you fish.
Me:
Bow, Crowsnest, Oldman and tribs, central AB brown trout streams. 1 SA box ~400 nymphs, 1 box stonefly nymphs, 1 box stonefly adults, 2 boxes streamers, 1 box general mayfly and caddis adults, 1 box mayfly emergers, couple miscellaneous smaller boxes of what I think might be hatching. One terrestrial box.
I might leave 2 or 3 behind on any given day, but I almost always have at least 4 full boxes. Seems like a lot.