I had some fairly old vanilla beans (about a year old), that looked to be in still good shape and added them to a bottle of Tito's Vodka.
By itself, the Tito's had a nice smooth taste to it, but after 10 days with the vanilla, a certain bitterness crept it. It didn't taste "off," rather more like cheaper vodka.
So, what would cause the bitter taste? Is that just somehow part of the vanilla bean experience?