Call me Lenny/LeniWhat's the greatest extent (as in the most amount of time) to which you've eaten something past its expiration date with the food still being enjoyable?
NekomancerButtermilk always seems to have like a one week expiration, but always seems to be fine up to maybe 2 months surprisingly
Assuming it’s cultured buttermilk, you can keep it going by adding milk when it’s almost gone, then leaving it on the counter overnight. It’s like yogurt but more robust, less fussy.