I am pretty ignorant on Whisky and am hoping someone can educate me. I have a bottle of Dimple Pinch 15 year old blended whisky that I got from my Grandfather's house when he died in 1991. For some reason, I have been holding onto it for 20 years.

My question is, does Whisky age in the bottle, like wine, and get better? Or does it have a shelf life? And if so, what is the shelf life? Thanks for the help.