It's been said by the best authority that you only need one fly...ever. And it's also been said that to tie or fish anything more than that, you're likely doing it much more for yourself than you are for the trout. Perhaps there's more truth in that than most of us would like to admit.
However, I submit that there are other worthwhile reasons to tie, and to tie a bunch of patterns. Sure, I tie (and fish) way more than one pattern. And a lot of that is done for purely selfish reasons like my need for peace and quiet, the relaxation that only a fly vise or a reloading press can provide, or the fun that comes from adding funky twists to established fish-catchers. But the one very rewarding thing that has come from my fly tying is that I also tie for my friends.
I have a tight knot of friends who have been with me through thick and thin. They've backpacked, skied, hunted, frozen, burned, fished, and rambled with me all over the Colorado Rockies. On occasion, I have entrusted them with with my own children in the backcountry. They would give me the shirts off their backs, and I would do the same for them. So, until the time comes to do just that, I'll be content to send them a handful of my flies from time to time.