Yeah, if I do this wrong it'll be extremely boring, although I think I can steer it into relaxing and maybe even cathartic. :) I'll need to figure out the balance between familiarity and change, but I think it can work.
I was thinking a full playthrough could be 20 minutes, and a character's life 5 minutes (maybe even less). With that length I can spend more time polishing. I think it's best if I encourage players to explore and jot notes reasonably quickly, but this game will definitely require experimenting with the pacing to find what's fun.
I have thought about puzzles and traps and think that could be fun, but players would need time to write codes/warnings before they die. I think I'll have to experiment with that once I start prototyping.