Just changed my mask after using the original one for a full year. It was still functioning fine as far as I could tell. But my air leakage rate has gone down quite a bit and my sleep interruptions are down about 50%. Maybe masks don't last a year.
I have a complete new head gear set and heated hose on hand. Other than the mask (which I've replaced), the year old set is still working fine.
I wash everything with tap water and Dawn about once a week. We clean the faucet before use as that could be a source of bacterial or fungal contamination. I have only used "ordinary distilled water" in the reservoir for the whole year and don't have even a trace of scale. I don't see a need for anything more elaborate than that.
