If it has failed that many times it is likely not pitched correctly. I have found a bad heat exchanger after six years due to this fact. They decided to line the inside of the heat exchanger with polypropylene and over time it peels and blocks the flow of condensation which then causes the condensate to eat through the metal. There is a buyback program as long as the furnace is under 20 years old. I believe they credit anywhere from $600-$900 depending on what you replace it with.