They don't float forever - any object orbiting at the altitude of the ISS will decay from atmospheric drag, generally on time scales of a few months to years.

They don't float forever - any object orbiting at the altitude of the ISS will decay from atmospheric drag, generally on time scales of a few months to years. Human spaceflights at altitudes beyond significant atmospheric drag would need another solution, but we haven't done any of those since 1972.