as long as there's no moisture in the jar you'll be fine. you can see the condensation on the side of whatever your using, i've personally never seen any in jars, but i know it's possible in plastic bags - for instance, putting orange peels in the mix with your weed could produce mold.

your weed should be safe for the most part - safe from everything, but you. smoke it already or send some this way. lol, happy smoking, man.

i never answered your question, directly. your weed can stay in there as long as you please, as long as there's no moisture.