Unopened distilled liquor can last many, many years...many whiskeys and whiskys are aged in barrel for a decade or more. That being said, they don't continue to age in the bottle - so while your liquor might still taste good, it won't taste any better than it did when it went in the bottle...and it might taste worse if it's been stored in sunlight. (So your 8 year old Jack Daniels is still just an 8 year old Jack).
If I found some in the back of the cabinet, and if they were sealed, good quality whiskey's and whisky's are something I'd certainly try...but perhaps in an old fashioned or something like that. If anything, the flavours are going to be dulled with age. It wouldn't be something I'd share with a guest.
Heat can cause a small amount to evaporate (even if sealed with a cork) so you might have lost some to the 'Angel's share'.
While I wouldn't hesitate to open a sealed bottle of whiskey, I wouldn't drink anything that old that is a cream-based liquor or anything with a lower alcohol percentage than 40.
That being said, since you don't drink, John, I'd suggest you have a whole lot of good drain cleaner!