I'll chime in here to share my 2 cents.
I did my master's degree with Ricardo Iznaola at the University of Denver '97-'99.
I am a firm believer that everyone has to follow their curiosity. This was a real Ricardo-ism too. That the best way to learn is to learn like a child, to try and figure things out that interest you, with a spirit of 'what if?' and purse a spirit of child-like curiosity.
As for 'to practice music or to practice technique', it really misses the point. Follow your curiosity, follow your teacher's advice. As an undergrad, I found that I would practice repertoire repertoire repertoire, all the stuff I was dying to play. I'd get through the required recital, and would look at my playing, and say, "ugh, my technique sucks". I'd work really hard on my chops for months, until I was dying for music, then I'd start the cycle over again. It was not the most even handed approach, but I stayed in love with what I was working on, and was always dying to play guitar.
Fast forward to my DU days with Ricardo, and I will tell you that I was a devoted Kitharologus practicer. 3 routines a day, 6 days a week. Each routine took 15-40 minutes, but heck, I had moved to study with Ricardo, and if he said that was the thing to do, I did it. Once I complained about it taking too long, and like someone mentioned earlier in the thread, he said to me I was doing too many repetitions. I was also doing them too fast and not in a controlled enough manner, so I learned to curb those impulses eventually.
I love the K-book (my pet name for Kitharologus) and will often recommend it to my adult students. Individual exercises only, no adult amateur I've taught has time for the full monty...
I also still work out of the K-book, but I also work on material from Sagreras, Tennant/Pumping Nylon, and repertoire excerpts. The fact is that when I was studying with Ricardo, he COMPLETELY revolutionized my playing. I was working waaay too hard, and he helped me discover a much finer level of proprioception. Working with just the K-book would NOT have fixed my playing. I would have just done the same cool exercises with my previous level of misunderstanding of technique. While I think one can learn lots from books and videos (YouTube is pretty amazing), everyone needs to sit with a master player/teacher to have their playing observed.
Read books, do exercises, play repertoire, love every minute of it! See a teacher if you're not sure!