I have a 1997 Ram purchased new. I just had the A/C evaporator replaced. This is the third one. The first lasted 2 years and was replaced by the dealer. The second lasted 4 years and was replaced by another repair facility. Both times I was told it was leaking. Is it normal to have it replaced every so often? Is there something I should be or not be doing to extend its life? I was wondering if anyone else has had this problem or am I just lucky?