i get new nebs for each treatment. and if i don't, i hide my old ones and they are forced to give me new ones.
the reality is that once a neb is used, it's full of a CFer's bacteria. if you store it in a bag or let it hang out without washinging it & boiling it to destroy the bacteria, the bacteria grow in the neb. then hours later when you use the neb again, you're breathing in the bacteria. counter-productive.
get a new med or each treatment. otherwise, why are you wasting your time in the hospital on anti-biotics???