Is there anything wrong with locating my Piano near a Fireplace or Hot-Air Vent?

Absolutely!

Pianos function best when the environment is as stable as possible. Minor variations are inevitable in all households, but by keeping your piano away from a heat source, you help keep those variations to a minimum.

By locating your piano away from hot-air vents, fire- places, woodstoves, and sunny windows, you let the heat spread out and dissipate as much as possible. If you can feel one spot on your piano that's warmer than another, you have a problem.

The same holds true for cold or moist air. Watch out for open windows in winter that allow cold air to blow directly onto the piano. Avoid putting the piano near a steamy shower or a leaky clothes dryer.