lostidlewonder you are a well dissiplined beast reading through your post had sweat dripping down my face 9 hours on 1 piece, but so true. Can you buy stamina in a jar?
I may try your aproach but not to that level. I think I would pop 
Don't think you would pop, you will definatly pop. I hated doing 9 hours a day solid practice. It wasn't by choice that I did it, it was forced upon me, a requirement from my teacher. At the end of the initial day my fingers where killing me and I honestly for the first time in my life hated the piano. But I always know when we are in situations which make us uncomfortable, situations which totally challenge us, this is where we learn things which will say with us for the rest of our lives and for the better.
I caught a glimpse of an amazing rate of learning, mind you I really honestly do not think I have the motivation to exist in this realm every single day of my life. I really do have more things in this world other than piano that I love to do. But when I am forced to learn things in a very short time I can do so because I have practiced learning at a fast rate. I know how to force the issue in my head so that my conscious memorisation of notes falls into muscular memorisation as fast as possible. This of course comes through tonns of repetition and logical thought. Not just senselessly repeating notes, but repeating passages and consciously observing notes which guide us, forgetting about them and then testing if we can appreciate what the feeling of the hands during the passage.
Wow. I admire those of you who have the discipline to physically practice for nine hours a day. Unfortunately my schedule won't allow that, so I have to settle for three.
I have been studying five of the etudes for about a month now and my elbows are absolutely killing me. Not sure if this is due to the etudes or to my other music . . . But I am playing a concert at the end of April and I can't take any time off right now.
Of course not everyone can devote the majority of their awake time to piano practice, it is a hermits life and most of us have other commitments and interests. But the Chopin Marathon of 24 etudes distance should be run in a 3 week period and this you choose do any time of your life, even if you have been practicing the etudes here and there for years. Although some of us make ourselves so busy we never can even have that 3 week honeymoon with the etudes.
There should be one point in your life where you say, I'm going to do this now, I'm going to study all the etudes, one a day, until I play through them all and can play through them all without using the sheet music. PLAY THROUGH THEM, not master them, and play through them could mean 1/2 tempo even. If you are a serious piano student you must study all the etudes in a brief time period, since they embody the entire piano technique as a whole. It is used for you to measure what you can and can't do well at the piano. The best litmus paper for your piano technique and musicality. If you spread out the study of the etudes over the years then you do not test yourself, you learn and grow with the music. We should use try to use the etudes as a test, we should know how to deal with the technique written within them and question why it is harder or easier in places.
This is so that we know ourselves as pianists better. We should study the Chopin etudes as a test for our piano technique and make adjuistments to our playing based on difficulties we face, we shouldn't use the etudes as peices to develop technique (although many people use it for this initially), we should already have aquired technique through other pieces but demonstrate it with the etudes.
And I don't think I'm an advanced enough student to be able to memorize them as quickly as you're mentioning, but I am still enjoying studying them.
Everyone can consciously memorise music at the same rate. I can make a beginner consciously understand what notes they have to play for the most difficult piece in the world, but what is the point? Their hands will not be able to follow it and it might take 2 weeks for them to aquire the muscular memorisation of one bar!
A lot of intermediate/advanced students I teach throw their hands up and complain that they learn music too slowly. Most of them say it takes so long to learn a little section even though their hands have
no problems playing it. This is where I sit down and try to understand the flow of Conscious memorisation- Muscular memory- Sound memory within them.
A lot of people neglect conscious memorisation of music. Sight readers for instance do not make strong conscious memoristation statements while they read their music. They simply read the dots and it cues their hands what to do, however there is no conscious observation of a note which acts as the centre of the hand, or a note which guides our memorisation of the pattern we must go through. There is no pattern recognition actually written down, it might be etherial in their heads, something that they sorta undertand but do not take that little step further to mark it down with a pen or highlight it.
Memorisers get too caught up in the actual fingers and notes, they neglect reading the score and advancing onto new sections using conscious observations as our guide. Sometimes I feel like it is like the Hanzel and Grettle fable, we make these conscious memoristations by dropping bits of bread through the score, but these may get eaten up by confusion in our heads, this is where we must also learn to backtrack and repair conscious memory points which are failing or we will get lost and eaten up oruselves.
Conscious memoristation of notes will vanish if it is not continuously restated again and again during our practice session. We must remind ourselves of notes which act as a balance to the hand, notes which define a pattern we play etc. We must lift our hands and put them down on notes simultaneosly making a conscious observation of notes and patterm in our head, we can even say it out loud which I catch myself doing a lot of the times. But at the end of a practice session these conscious memory statements should be pushed out of our minds and we should be able to appreciate the muscular memorisation of the passage. This should be done straight away, do not ever leave the piano with conscious memorisation still in your head because this will be forgetten and you will forget a lot of work. Only stand up once you have attained muscular memorisation of a passage this is long lasting.
Some people never consider this flow of learning, they just let it happen instead of controling its progress. Try to understand how to move from conscious memory to muscular, once you do that you really push your rate of learning, you will feel like you have control over what you learn then. Sounds all nice in words but in reality this is really tough, to understanding how we learn is very hard and sometimes we can't understand it without a good teacher or taking on marathon study tasks.