I don't think that most whiskey will go bad. My anecdotal evidence for this is a bottle of SMSW that my father-in-law has: a 12-year-old Ladyburn. Now, that distillery has been closed for decades, so that bottle is at LEAST 15 years old, and probably older than that, and I strongly suspect it has been opened for most if not all that time. This bottle could easily have been opened twenty years ago. There's about half a bottle left at this point. I had a bit on Monday, and while not the best Scotch I've ever had, it was pretty good---certainly still drinkable. Meanwhile, in my own collection I have a bunch of bottles that have been opened for up to three years or so now and I have not noticed any deterioration in any of them.
P.S. For any Scotch fans curious about the Ladyburn, which is a very rare item nowadays, it was light and surprisingly fruity---not grassy like other Lowlanders I'm more familiar with. It had a sort of citrusy quality to it.