Orbital debris do have decaying orbits, but they can take quite a while depending on altitude (with estimates for a existing systems in LEO anywhere from severa

Orbital debris do have decaying orbits, but they can take quite a while depending on altitude (with estimates for a existing systems in LEO anywhere from several months to several centuries): http://www.nasa.gov/news/debris_faq.html http://www.nasa.gov/news/debris_faq.html