The bag in ours is disposable if you wish and only costs about 100€ for one replacement, but if you just hose it out it almost has a lifetime warrenty. i.e. if it goes wrong it kills you?
No, to be serious, all I do is to hose the heavy duty cloth bag out and it will last forever, or as near as. If I don't have time to wash it I just dump it in a bucket of water and do it when I do have time. So far it has given us 5 years of good service and as it is a 2001 mode, about 8 years old-ish. I have replaced the tank tracks and reconnected the cable by chopping a few inches off as it was getting a bit worn. Remember that I am a lekky.
Good bit of kit!
Never forget that you are unique, just like everyone else.