Your bottles of whisky should be just fine - however, keep in mind - as I tell everyone, it is trial and error. If you decide to keep them to yourself to enjoy, once opened, smell it and go from there. There can be situations which may have affected the spirit after being stored for 30 years such as air seeping in (this can happen to even the best sealed bottles), deterioration of the cork which itself may flavor the spirit and if a metal cap is being used, that too may deteriorate over time possibly causing a metallic taste.
If you want to have them valued, contact Bonhams.com or McTears.com. If you are US based, let me know and I'll give you some names of who can value your collection. Also, keep in mind that if you want to sell your collection, unopened bottles are always worth more. And, one last note, no - whisky does not improve or mature with age - maturing stops once it is taken from the cask and bottled. So, for example, if your whisky was matured for 12 years and then bottled - no matter how many years you have had it - say for example 20 years, what you still have is a 12 year old bottle.