If you really want to hold onto some weed long term...
Where I grew up I had a friend who grew his own. This was in snow country, so he'd freeze gallon size freezer sacks of bud to smoke over the winter. He was very careful about getting all the air out of the bags before sealing them, so the stuff was always great when he 'thawed out' a sack!
I watched an infommercial on TV recently that showed a shrink wrapping system (for food) that pulled all the air out of a freezer bag and hermetically sealed it. The first thing I thought of was my 'ol buddy up North. The more air you can successfully remove from the bag prior to freezing, the less chance you'll get mold or ice crystals forming on your stash.
If you are serious about long term storage, you may want to keep an eye out on TV for that shrink wrap system infommercial. If it can keep a piece of fish fresh and freezer burn free for a year, imagine how fresh it can keep your buds!!!
*Another tip: If possible, store your buds in a freezer that doesn't get opened very often. Your refrigerator freezer probably gets opened daily like mine. Opening the freezer daily lets in warm air and moisture, which can form ice crystals on and inside your bud bags, which is the last thing you want!
If you try this and like the results, let us know.
PS: Mason jars in a safe at room temperature is a bad idea. Thats asking for mold/fungus to form in the jars dude.