ganymed
well, the first thing you should know is that I learned the etude 3.5 years ago, and while I haven't practiced it everyday since then (obviously...), it is really the time it takes to learn a piece like this - for all pianists, I guess, if you're not Liszt who was able to sightread all of op 10 perfectly. I still feel I have a lot to work with, but having recorded the piece I want to move on and learn other (easier!) etudes and focus on that. This etude is so good for building up endurance and power, but it can also be damaging if you practice the wrong way.
Practice without pedal, possibly without bass notes too in the beginning. Every note must be distinctly heard - a lot of students make the piece sound "blurry". Do it very slowly at first, and maybe mezzo forte. Now that I've played it for a while, I often practice it super slowly and FF on every note - it helps in building up endurance, but also in making every note heard.
For speed, I suggest to sometimes practice very slowly (contradictory or what?!) but with fast finger motion. In other words, with the fingers not playing highly raised, striking the key from a distant position.
Another problem you're likely to encounter is that the 4th and 5th fingers aren't working as good as the other fingers. I use a rhythmic variant to help strengthening them:
The arpeggios are written out like this: C G C E etc etc. Instead, play in 16th-triplets: C G C E C
Hope it helps!"