Last year an HVAC repairman came to look at our original-to-the-building 1986 unit; he refused to work on it because it was too old. The next guy said it was indestructible and will last us forever; the next time we turned it on smoke started coming out of the vents with a burning smell. The third guy also said it was indestructible, but not before insulting the electrical work of the second guy. So now so far so good.... but we'd very appreciate any contributions in case of failure