Cognac Brown

Shelf life of whiskey, vodka, gin etc.?

I found some dusy opened bottles of gin, brandy, whiskey, crown royal behind a shelf in my grandmother's house. What exactly is the shelf life of vodka, gin or brandy after it has been opened. Are they any good after many years of sitting? I heard that brown liquors such as brandy, cognac or crown royal will get some people sicker as opposed to white liquors like vodka, gin that I heard doesn't make people that sick. Is this an urban myth? I want to use the gin in lemonade or make a screw driver, but is the potency gone out of the liquor. I found one bottle of brandy that has the seal date of 1971 and it is half full. I don't think I would drink that. But I would like to know about the gin.

As long as it's been sealed, it should be fine. That stuff lasts FOREVER.

BL01 Roll Bonded Leather Hide Upholstery Fabric 10 Yd 54 W Sauvage Cognac Brown
BL01 Roll Bonded Leather Hide Upholstery Fabric 10 Yd 54 W Sauvage Cognac Brown
$95.00
Time Remaining: 28d 7h 43m
Buy It Now for only: $95.00

BL04 Roll Bonded Leather Hide Upholstery Fabric 10 Yd 54 W Windsor Cognac Brown
BL04 Roll Bonded Leather Hide Upholstery Fabric 10 Yd 54 W Windsor Cognac Brown
$95.00
Time Remaining: 28d 7h 44m
Buy It Now for only: $95.00