[bkberry352]

Answered in their FAQ[1]:

> Decommissioning by boosting an object to a higher “graveyard” orbit to extend orbital lifetime is often done with smaller satellites operating near geostationary orbits (~36,000 km in altitude). This is not a realistic target for space station decommissioning because of the large mass of the space station and distance from its operational altitude to a “graveyard” orbit. Existing propulsive assets (spacecraft) do not have the capability to raise the space station’s altitude to such a high target.

[1] https://www.nasa.gov/faqs-the-international-space-station-tr...

[wongarsu]

For perspective, the ISS is currently orbiting at 400km altitude. Typical graveyard orbits are just beyond geostationary, so lets call it 36500km.

Orbits get somewhat emptier beyond 2500km altitude, but you'd still risk spent rocket stages or defunct satellites hitting the ISS if you don't go all the way out beyond geostationary. Maybe you can stay at lower orbits if you dock a vehicle that can provide thrust for obstacle avoidance even after the main station powers off.