Butter literally sucks the odors and flavors out of the air and holds them.
That said, keep your beautiful homemade butter well wrapped and consumed within 2 weeks. It is best fresh and within a few days. (It's bad when it sours or smells like onions.)
I don't think homemade butter has a chance of long shelf life because it is so darned good! (Like the question of how many licks does it take to get to the center of a tootsipop.)