People will tell you that one of the benefits of spirits is that they don’t expire. But that isn’t totally true. Yes, spirits that are in unopened bottles that have remained sealed are still safe to drink even decades later. But if the bottle has any added sugars, flavorings, fruit juices, cream etc., you’re probably best off dumping it out — it likely won’t be as good as a newer bottle and no one wants to drink that old Baileys you found in the back of your grandparents’ liquor cabinet anyway.
When it comes to an open bottle of liquor, it is true that the spirit won’t go bad as quickly as an open bottle of wine or beer will, but oxygen will still get in and do its thing. That doesn’t mean an opened bottle of straight spirit, such as vodka, whiskey, gin, or tequila will go bad. It just means that after a few years of sitting in an open bottle, the flavors may begin to fade a bit. If the spirit has cream in it, though, after sitting open for a year and a half, you need to toss it. Your stomach will thank you.