Yes

Al

Yeah, any place dry and cool is fine. Just seal the bag back up so it stays dry.

I keep my 50 lb bag in a plastic tub with a loose fitting lid. It is out in the weather and though the container is water proof it is not sealed. It does not seem to collect moisture from the air and varying temperature summer or winter has had no affect. Al

Powdered dolomite if kept unwet (don't worry about humidity) and below about 1000 degrees C (that part will be easy) would last until the end of time.