Can’t speak for large scale sites with abundant volcanic activity… But for residential geothermal the bore hole has a lifetime based on how much ground water there is and how active usage it sees.

This is because using it cools the hole slowly and after a few decades (depending on how quickly ground water can dissipate heat gradient) a new hole need to be drilled a distance away.

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analog31 2 days ago | parent [-]

Can we cycle the holes? Use one while the other one is warming back up.

	▲	Y-bar a day ago \| parent [-]
		There are some modern heat pumps which can put heat energy back into the hole during the warmer season when the pump acts as a (cooler). For my own Daikin pump this would be possible if I had a different flooring than wood. "Unfortunately" I choose wooden flooring on my heated floors. Cooling this means that the I risk condensation due to moisture build-up and therefore a long-term risk of mould. But I have only need of cooling 1-2 months of the year, so it is not a big deal, I can solve it by clever use of insulation instead. But for those able to use a geothermal pump like this it also has the short-term benefit of increasing the effectiveness of the hole as well.