Generally, masks and tubing should be replaced every year, however this will vary based on your skin type, daily usage and mask fit.
Replace your mask or tubing if you experience or notice any of the following:
regular pressure leaks
tightening your headgear/mask to avoid leaks
cracking or hardening of your mask's cushion or silicone
cracking of your mask's hard, clear shell
pressure sores or redness at the bridge of your nose, upper lip or cheek that does not go away after removing your mask for 10 minutes