Don't know what your problem is, but my earmolds are clear white. I wipe them off daily with HA cleaner, and put them to bed in a dryer. I am not sure what they are made of , they are a hard materal but they have not shrunk. I got my Naida's last year and my audi said they were fine and I didn't need new earmolds. I have been wearing BTE's for about 15 years and this is just the second set of earmolds. Maybe my audi knows something you don't?
The material contributes a lot to how often your molds may need to be changed. Hard molds, which are more commonly used in milder degrees of loss, are less subject to aging. They tend to last longer. If your molds are made of one of the soft materials they may need to be replaced every year or two due to shrinkage, becoming brittle, etc. Regardless of the type of earmolds, as many have said, tubing may need to be replaced as often as every 6 months.