Wow, is this what you conservatory people have to do?? Two hours of technique every day before you can work on your pieces? I'm impressed, although a little horrified at the same time. I think definitely DON'T emulate Clara Schumann by amusing yourself with a book while working on technique. If you don't watch and listen to yourself, you won't know whether you did it well, just whether you did it. We're musicians, we work with SOUND, we have to pay attention to our sound all the time.
Philosophically I like the idea of using pieces to work technique, and that usually works for me, but I'm (almost) old, so I've been playing scales etc for a really (!) long time. I don't know, for someone with less time in, probably some very specific practice would be helpful. No etudes, though, unless they're beautiful and performable. I don't see doing every single scale every single day unless you don't really know what the notes are for each scale (or if you're going to be mercilessly tested on them in public, that's kind of a good reason, too). So many of the physical patterns occur in several different keys, and if a particular motion works for you, then the scales that use it should be in good shape. I know my weak keys, and I also have two stamina exercises that I try to get to most days. Josef Hoffmann said that if you can't play your exercises, you'd better practice them, but if you can play them, he didn't see why you have to be everlastingly practicing them. Hm. It depends on where you're at. But as I said, I'm not in the exam cycle that many posters are in; maybe they don't have the option to just (mostly) play pieces, I don't know.
The key-of-the-day approach by nomis is good. I use that on another instrument that I have less-developed technique on. I have a short but thorough cycle of things I do every day (well... not quite) in one key.
Topic: Scales and Arpegios *shivers*