It's not the orbit boosting that should concern us, it's the innevitable deorbit burns.
We have to think about it and debate it sooner or later.
The final ISS configuration will only last so long and have to come down
eventually, like MIR.
Innevitable budget cuts in the coming decades, creeping obsolesence
and structural and hardware breakdown and wear will bring about
its deliberate demise as happened to MIR.
But unlike MIR, we're talking about something two football fields long and
containing several hundred tonnes of mass.
And computer simulations as to how to carry it out safely have limitations.
Jacob