Mandy
I use disposable ones too, but I have been told that as long as you wash them in hot, soapy water (or the dishwasher) after each use that I can use them for 2 weeks and then replace them. You may be using a totally different kind, though. Mine are the old "T" style, my particular brand name is Salter Labs. I started using these to help reduce foaming w/ Colistin and although I don't do Colistin any more, I guess I've just gotten used to these types.
The PARI, etc are better, but my insurance only covers them at certain medical equip places & they are all miles away, so I just use the disposable ones.
I'm not sure what type you are using, but it sounds as if it could get expensive replacing them every day.