Yes the wadding does degrade over time, and it depends on how heavy a user you are, they can be rinsed out, and dried in paper towel and re-used, but they do get pretty scruffy eventually. It could be a week to several weeks depending on usage.
You could buy wadding from a aquarium shop, it is the material used in pump filters, it's called Fluva or Fluval, I have never bought it personally, but I'm sure someone that has will give you the exact product details, it comes in sheets and you can cut it to size, it's pretty cheap and a box will last forever I imagine, lol You just have to make sure it is not
the charcoal impregnated type
You could try a search for "Fluva" or "Fluval" in the forum.