I agree that, assuming the seal hasn't been broken, your whiskey is PERFECTLY GOOD to drink!!! Even if it has been broken, in all likelihood the whiskey is just fine.
Although time can eventually have an effect (oxidation by contact with air over a LONG period or evaporation), it takes a long time assuming you've not left the bottle open for all that time. Whisky is pretty stable. It's preserved by alcohol, after all!
However, don't make the mistake of thinking that your sealed bottle has "aged" over the years. Whisky aging takes place before it's bottled, still in the barrel. It doesn't age at all once bottled (as opposed to good wines).