i bought some carnuaba wax about 9 months ago - it was on sale, and so i bought and just started using it......
i only wax 2 or 3 times per year, so the bottle will probably last me 2 or 3 years.

Does wax have a shelf life and what detriments are there to have it sitting in your garage thru the seasons?

i can't see myself going thru a bottle every few months.

Well it depends in large part on the environment that it's being stored in. Some carnauba's suggest refrigerating them to prolong their lives. I think it'll become apparent when/if it's gone bad... It'll start to get dry and crumble. Better waxes today last alot longer than they used to though. Try to avoid excessive heat or cold for your typical wax.