[Porsche-O-Phile]

I picked up a bottle of cognac XO the other night but as a relatively new person to finer liquors (I've traditionally been a beer/wine kind of guy) I'm not sure if it's like a wine or a liquor. Should I wait for an occasion where I can serve it and use the entire contents in a single evening or maybe over the course of a day or two, or is it okay to open, enjoy a little and then re-seal the bottle for another month or two until the fancy hits me again?

Just curious - like I said, I'm new to this stuff. I like it, but being that it's expensive, I don't want to waste it either.