boooooooooooooooo liaaaaaaaaaaaar
i bet it is good in pan sauces, but i don't think it lasts longer than white wine. my friends and i were all just complaining about this. every time we see vermouth in someone's liquor cabinet and crave a martini, we're always in for disappointment. it's always gone bad.
ime it lasts like a month unless you modify the atmosphere. i've never tried in the fridge, but maybe that helps, too.
maybe the actual kitchen hack is: old vermouth can be used in pan sauces instead of tossed or left in your liquor cabinet to taunt your guests? idk