How long can you reasonably expect a geo-thermal heating system to last before replacement?
 
I just bought a house last week that was  built in 1991 that has a Geo-thermal heating system in the basement, so the system is roughly 17 years old. Three days after settling/closing on the house, one of the metal brackets on the blower moter gave way, so the blower was spinning up against the frame assembly. I called a repair tech and he gave me a price of $600 to replaced the fan/moter assembly and 8k to replace the geothermal unit with a newer more efficient one (or 10k for the best one available). The system is a open design where it pulls the water from a well, the well, pump and plumbing are fine, he said it was oversized for my requirements. (They used to use the well for drinking water, but it is now city water). The replacement cost is somewhat of a shock, I expected 5k at the most, since the rest of the system is fine. If I just have the unit repaired, I'm wondering how many years it could last before something else failing on it.

Another question I have is, is it normal to have a seperate heat exhange / blower unit for each floor. There is one in the basement, but it only handles the first floor of the house. The second floor currently runs off a heat exchanger unit, that we were initially considering changing to Geo-thermal.  It just seems excessive cost to me, if a geo-thermal system requires one unit per floor and each one costs 8 to 10k each (excluding installing the ground loop) and they only last 17 years. In your experience, how long does it take to pay for themselves, with cost savings? 

If the unit is still working why would you replace it? Just take the bracket to a welder and have him fix it for $20.

If it was just the matter welding the bracket, I would agree, but the fan fell into the housing while running, it ripped up a section of the casing most likely throwing the whole fan out of balance. Even if I could just weld it and it worked, the fan would proably wobble like hell, making the next failure highly likely in the near future. I had the repair tech replace the whole fan/motor/housing with a new one, it set me back $660. The system is running fine now. Interestly enough the repair guy said the motor was welded to the fan sometime in the past, he was suprised they were able to line it up good enough so it didnt wobble, perhaps they didn't, it may be why it failed now.

The geothermal guy said the unit I had, from 17 years ago was more reliable then some of the units they made only 10 years ago, something about compressors failing, so that made me feel better. I was just wondering how long I could expect the unit to last, so I know how much time I have to save up to have the money to replace it. Although I do not plan on replacing it before it's dead, I would like to have the cash on hand to fix it when it does. Nothing last forever.