Following on a bit from my other thread, over the years I've built up an enormous library of sheet music and teaching materials, but the more I look at it, the more I realise that I don't use half of it. I'm lucky that at the moment I've got enough room to store it all, but that might not always be the case.
It's an interesting question isn't it? Whilst our pupils might use a lot of the books, do we actually use them? (i.e. we show them our copy, they buy their own, ours goes back in the shelf) Quite often, I'll have bought an alternative piece for an exam and after that, the book's never seen the light of day again (and the pupil probably didn't use it anyway!) - now of course with YouTube and to a certain extent with the AB downloads, we can now listen to all the pieces before choosing/buying.
I suppose I'm thinking mainly piano because I don't need books for accompanying. Obviously, duets, exercises, technique books etc. are all useful, and I'd still want to have copies of tutor books (though where possible I buy the versions without the CD!). OK, it's nice to be able to go and browse to find something suitable for a pupil, but even after browsing, the book just goes back in the shelf. I'd probably better spend the money making an occasional trip to a big and really decent music shop (if any still exist!).
Obviously it's nice to be able to have things which we can just pull out too use on an occasional basis (they've finished what we're doing, they've left their music at home etc.; duets etc. too), but do I really need my own copies of Up-Grade!, Step it Up!, Piano Time Pieces, Music Through Time, Time Pieces etc. etc. After all, I'm not likely to play them. Of course, with Musicroom and Amazon, you can now 'look inside' a lot of these books. Having had them all, I know what they're like now.
It's taken me 10 years to realise that I've probably been too generous in gathering together lots and lots of books so that pupils have a wide choice. Anyway, I'm just wondering what others do (personally I'm sensing a big clearout on the horizon for me)