I have a forced air heating system with the supply vents in the ceiling. Someone told me that in the winter, the returns should be near the floor. Any suggestions?

Since heated air rises it would be better to have some supply at the floor level. You can somewhat mitigate the problem by switching any ceiling fans to blow up. If you have a basement, adding lower supply ducts should be relatively easy. Slab house are much harder.

I have an addition with a second floor, and the heat vents are in the ceiling on the second floor only. All venting goes up one chase. Is your house designed so that moving returns is even possible without extreme changes?