Basically what happened recently was that the oil company which i have a yearly contract with came out to do their yearly cleaning of my oil furnace in my house. The cleaner discovered that my heat exchanger needed replacing and was damaged, due to some water damage it seemed. After cleaning out the furnace and doing his basic checks and repairs, he informed me that i needed a new heat exchanger, but since the furnace looked relatively new he said it was probably under warranty and would cost the basic contract labor (400-450 dollars) to fix everything.. flat fee.
Now one thing he also said was that it seemed that previous techs hadn't cleaned the furnace well in previous years, he saw and removed a lot of "built up stuff" in his words and was pretty sure the previous techs had did a half-hearted job in the yearly cleaning.
Its an old house, and i've had water leaks before so having water damage in the furnace wasn't unheard of. I was just wondering if not cleaning a furnace well would lead up to, or exasperate such heat exchanger problems. Or would bad cleaning only diminish the furnace's output. (less air flow, etc)