I have found through various sources that the Prius requires more
energy to manufacture than most other cars...but that it recovers this
energy deficit through lower energy use throughout its operating life.

What I can't seem to find, however, is...exactly how long does it take
(or what distance must be covered) to balance out that extra energy?
I can't imagine it would take the entire service life of the
car...what a shame that would be. And I know that in a lifecycle
analysis, the energy used to manufacture a car is far less than the
energy the car will use in its operation. As a result, even a small
improvement in economy makes a big improvement in the energy footprint.

So would anyone happen to know at what point the Prius earns back its
energy deficit, beyond which the energy savings are "gravy," from the
standpoint of the world?