re: Hypothetical question
I can't give you exact figures, but the short answer is a long time, thousands, but not millions of years. Geosynchronous birds drift slowly off station due to the fact the earth is not a perfect sphere and it is precessing. and because of the pumping effect of the moon's gravity. There ARE two spots on the equator where satellites would tend to be stable, one is at about 115 deg W Longitude, the other I do not recall from when I last researched this. All other orbital positions are slightly unstable and satellites placed there would eventually drift away.