How long can you keep Vermouth in the fridge . . .

[Obsessed]

. . . after opening it?

 

[clubman]

It's best within a few weeks, starts to lose its zing after a month or so, but it still drinkable after that. Red keeps longer than white, I've found. Unlike open non-fortified wine, vermouth doesn't really go off or anything, it just becomes less and less peppy. I find I generally end up increasing the amount of vermouth in a given cocktail as the bottle gets older to compensate for the diminishing flavor, which has always worked fine.

The key, of course, is to get the small bottles - but unfortunately, all of the super fancy brands (Vya, Carpano Antica, etc.) come in big bottles only... probably best to throw a party around one of those!