That's an interesting idea TNL. Be sure to purge your lines with propane before refilling a bottle so you don't push air. It may be difficult to get a consistent fill into a propane can though. They have single port valves with no overflow features so you can only transfer liquid until the pressure equalizes between the tank and bottle.
IMPORTANT: be sure that a gas space remains in your bottle. If you manage so fill it completely with liquid, with no gas space, you will subject the bottle to pressures exerted by the expansion coefficient of the liquid. A single phase fill (only liquid) can exert very high pressure when temperatures get warm. Luckily disposable propane bottles have a pressure relief valve so you probably won't blow them up, but you'll have a propane leak.
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