In article , -MIKE- wrote:

Correct. There is only so much moisture in the air and only so much air
in the bottle. I'm guessing, if you used it once or twice and left the
3/4 full bottle on the shelf (like me) for two years, it would be
virtually new.

This discussion got me curious. I just went down to the shop and checked my
bottle. It's about 2/3 full, and the label says "Best if used by May 31 2006".

I last used it in early October 2008, and it cured just fine. No problems.

Storage conditions play a large role, I'm su my shop is in the basement, so
the temperature doesn't vary too much from 70 degrees all year long, and
there's very little sunlight exposure. And I run dehumidifiers in the basement
year-round, so that part of the environment is also well-controlled.