The ISS is boosted to a higher orbit every few months using on board thrusters, otherwise atmospheric drag would have deorbited it a long time ago.
But the hardware will not last forever, it has taken a beating from micrometeorids, radiation, extreme temperature changes etc. At some point it becomes too risky and expensive to operate.
I didn't mean to keep operating it, but to use it for spare parts or as a container, to shield new gear from those perky micrometeoroids.
The ISS must be ~ 2/3 (?) of escape velocity and out of the densests layers of the atmosphere, so it seems reasonable (to me, at last :) that the power needed to boost it is much less than what it took to put it where it's at.
GEO is very densely populated, maybe a repair shop in the neighborhood would attract some customers.