Just out of curiosity do you have a Computer model or Mechanical unit? Is it 2 tanks or just a single cabinet unit? Is it protected from the weather? And is it the same problem or something new?
On the RO the membrane does not have to be changed yearly. Its normaly 18 months to 5 years I don't change my filters until it taste funny! It all depends on the amount of water you drink. make sure you maintain your filter as needed meaning backflush it once a week.