I currently have two fly boxes that I carry to the stream when fly fishing trout and grayling.
A few years ago, I had something like 4 - 6 fly boxes. It has been a part of an attempt to Lighten the Load as in John Gierach's essay.
Number of fly boxes is one thing, the number of fly patterns is another. I haven't counted how many fly patterns I have in my two boxes, yet I think that there are too many of them. And at the same time I think that I still lack a few. Strange, isn't it?
If you look my smaller fly box, you may notice that it has some discipline in it. There are free living caddis larvae patterns in different sizes and colours, Gary LaFontaine's Sparkle Pupa patterns and some POPA Caddis patterns by Oliver Edwards. Bigger box has less uniform selection of dry flies, streamers and big nymph patterns. That is because I put the content of my old streamer box and dry fly box in single fly box. But also the number of flies in specific size and colour variation of pattern is not as disciplined as in smaller box. I'll have to work with that next winter.