I practice about 2 hours a day. I practice in blocks of 20 minutes. Before I even practice, I write down what I want to accomplish for the day. This saves a lot of time, and I believe those who practice more than 3 hours do not do this, resulting in the exremely long practice sessions.
20 minutes: Scales of any of my pieces. So for example, if I am practicing a piece in C major, I would do four octaves of CM, Cm (all 3 scales) in contrary motion, Octaves, and arpeggios (contrary motion). If I get stuck on any of the scales, then I might break it down for the week.
20 minutes: 1 movement of a sonata (usually the one that needs to be worked on the most)
20 minutes: 1 or two pages of an etude that needs to be worked on.
20 minutes: Brahms Intermezzo
20 minutes: 1 or two pages of another etude.
20 minutes: Another Brahms Intermezzo
20 minutes: Whatever needs extra practice from above.
After this, I take note on what I practiced for the day and what I learned really well. Then I make a list for the next day.
On the weekends I practice everything that I have practiced during the week, so obviously that would take more than 2 hours.