I prefer the volcano high over my other methods. I just bought the traveling case online the other day, lol. It comes with 1 extra bag and I was told to replace it at 100 fills or when it leaks. I'm over 100 bag uses, so it'll need it soon. It has changed color some and has a layer of film built up near the entrance. You can use regular oven bags they say ...

From the FAQ here:

7. Which parts of the Volcano inhalator are subject to wear and tear?

First of all the balloon, which has to be replaced by a new balloon after cleaning the valve set in regular intervals (after 50 - 100 balloon fillings). The balloon used is a Melitta (R) Toppits Bratschlauch Type "extrabreit". (Melitta (R) Toppits oven hose - type extra-wide) . You can purchase that product in many drugstores and supermarkets at a low price or on direct order from us. A roll with 3 metres of this product is enclosed with each Volcano, which is sufficient for 5-6 balloons. You may also use other oven hoses or oven bags, e.g. in the U.S.A. use Reynolds (R) oven bags Type "large".

By far less seldom (approx. 1x per year in everyday use) it may be necessary to replace the filling chamber screens. Each complete set is furnished with 3 top and 3 bottom screens. That will last a long time. No other parts are subject to wear and tear.