I just started this playing this piece and I like it a lot, but there is just one huge obstacle with this piece- endurance. Seriously, how can I build up endurance to play this piece by February. Without taking any repeats, I can play through about 3/4 of it. With repeats, I can play through about 1/2 of it. I`ve been playing for about 5 years, and man, this is a hard piece.

yes its difficult for endurance, I have played this piece 3 month ago.
I can`t very well help you, but try to play all the piece all day.