Do you need them? I can't remember if you go to class or do this yourself!
The battery went in mine a few weeks ago and I deliberated for ages about replacing it, I did and now wish I hadn't as I keep hopping on them and that's not like me! Also, I have to hide them each day as DD keeps getting on them and announcing she has lost/gained weight. She is 11 and I don't think that's a good thing.
Anyway, if you don't need them, don't replace them hun, it will do you good!!