Fatigue - You're going from 1 hour to 3 hours, that's an increase workload of 200% there is obviously going to be some muscle fatigue, topped by the fact you're attempting a piece more difficult than you've ever attempted.
Key is to learn it slow but w focus on musicality and analyzing your bodily movements during them. I have had learned exactly those three chopin pieces to a point myself as well and have learned much about technique and about musicality. Contact me if you want/interested any specific advice or experiences I can share w you regarding this piece.
Yes, you have learned them--- but these were not 'your first rodeo' at the piano. Just curious if you are concerned about the OP jumping right into a Chopin etude teacherless? I am concerned about proper hand position, possible injury. Your thoughts based on your experience with these etudes, and how that would translate into a returning pianist learning them alone? Yes, he played previously but, not only was that a long time ago, there was not real mastery of the repertoire he played.
All good points. No offence to the OP, but it would not be sensible to take this post seriously until some substantial amount of repertoire heading to that difficulty has been mastered. We've all gone through the those pieces that we loved and almost wished we could learn by investing time alone, but that always ends in tears.