I have never worked on 48/1. I remember trying to play through it as recently as when Sandro submitted it (which some of you might recall, as his interpretation sparked a few flames). I think that was about 2 years ago, and I might have tried it even more recently (like about a year ago). At that point, I still felt like it would be immensely difficult for me. I have read through it again recently after having worked on a good number of more difficult things (mostly Bach, but also recently Chopin 25/1 and 25/11), and I think that I might be able to do it with not too much work. It might be a little while, though, because I'm working on a recital (which will have etudes rather than nocturnes, and one of those etudes might be 25/10, which would be a nice prelude to working on 48/1).
55/1 has been more work than I anticipated. I played it when I was young, but now that I'm older I realize it requires a very mature pedal technique and also contrapuntal fingers. The actual fingerwork isn't so difficult (especially after playing Bach a lot), but getting the pedal just right has been a lot of work for me, partly because I'm using the sostenuto pedal a good bit, and partly because my pedal technique is weak to begin. I'm trying to research Chopin's pianos, and the pedals in particular, but part of me doesn't really care if he had a sostenuto pedal then or not (in the same way that I don't care that Bach didn't write for piano, or pedals at all). There are several opportunities in the piece to make something better by using it, so I shall.
In any case, the pianos as my school are all in bad shape right now because the AC was broken for over a week. I noticed earlier in the week that our piano technician seemed to have taken a vacation, as he wasn't around (I was looking for him because the good Steinway is horribly out of tune, and I won't record on any other piano while I have access to that one), and now I know why he was so angry the last time I saw him. He was working on the piano that I use most often to practice in my teacher's office and he did NOT look happy about it, and I apologized to him for banging on it all the time while practicing Chopin 25/11, and he said, "No, there's nothing
you can do to hurt this piano." I was thinking at the time that I know that isn't exactly true, and wondering if he was implying that he thought I didn't practice very often. But now I know.

So all the pianos have gone wonky due to the high humidity and heat, and when the piano technician comes back he will have a lot of work to do. I am hoping that I can convince him to start with the good Steinway so I can get some recording done, but we will see.
That brings to mind a question: how do you Euros keep a piano in tune in the summer with no AC? I know it gets hot there.