How do utilities with no expected life of their service amortize?
e.g. phone company offering pre-paid service as it is hard to realize revenue if there is no real-time detection.

If they just do it based on previous estimaged usage, which is reasonable, then how do they reconcile differences between actual and expected utilization?

one way of amortizint it is by first estimating its useful life in hours. Once it is done, the rest would be easy, just base your amortization by multipliying no. of hours used to its amortization rate.

Cost/expected usage in hours=amortization rate.