I haven't made weed butter, but id imagine it should keep for a really long time if there's a layer of endistrubed butter on top. Covering stuff in fat is an age old method of preservation.

Sorta. Anything fatty tends to pick up flavors from the environment. Now, in the cold, those chemical reactions are slowed down, but they're not stopped. If you leave it there for a while, it'll pick up off flavors. Still generally safe to eat, but you won't like it.

It gets dry and unpleasant to smoke, but the "quality" is actual drug doesn't really go bad or expire.

It can last for several years after harvest if preserved properly (jarred for curing and occasionally burped)

Yea the cannibanoids break down in heat and make the high less fun and more zombie/sleepy after a year or two. There is also risk of mold or going too dry depending on storage conditions.

Joints (fingers, elbows), lower back. Relieves pain and symptoms. Plus it's just made with coconut oil so you can actually bake with it, lol.