I have more collections on my K3 than most people would probably think is sensible.
In fact, I have more collections than some people have BOOKS on theirs. I have lots of genres (including genres just for short fiction), four or five favorite authors with their own collections, six or seven series collections, and the lists I mentioned. I think the total is more than 60.
It's just one of my quirks. The rest of my life can be total chaos, but my books are always well-organized (or over-organized, actually). It was the same with my paper books, so it just kind of translated over to the ebooks. And I gotta say, tagging in calibre is a lot easier than physically moving paper books around.