@KoiwiGal - I tend to use sleeper earrings almost all the time on my cartilage piercings. I only put in more fancy earrings when I'm going out, or want to dress up for another reason.
I think it's just because of the way they are situated, but they can get irritated really easily. Hair can get caught in the earring and pull, or they can dig into the ear when you are sleeping and roll onto them.
I just found really nice rose gold stud earrings to put in that sit very flat so I can sleep on them and everything and they work very well as sleeper earrings.