Comment by mapt

Yes. In a lot of historical spaceflight programs, the stage used in the upper atmosphere stayed with you to the final orbit, and was detached at low speed there. This saved you from having to design your satellite with significant onboard propulsion. Some of the upper stages were able to vent remaining propellants or pressurants, some were allowed to heat up until the pressure vessel exploded.

Suffice it to say this is not sustainable for megaconstellations in thousand years orbits. The responsible thing to do with that kind of scale involves reliable, redundant, prompt de-orbit of upper stages, and ideally for high-thrust, high-mass, high-engineering-margin-of-error atmospheric upper stages never to make it that far into the mission.