U.S. Dept of Energy reports there are many benefits to geothermal heating systems. Because GHP systems have relatively few moving parts, and because those parts are sheltered inside a building, they are durable and highly reliable. The underground piping often carries warranties of 25–50 years, and the heat pumps often last 20 years or more.

http://www.energysavers.gov/your_home/space_heating_cooling/index.cfm/mytopic=12660