Cherish that Grandpa- never really knew mine. 
Same here, my paternal grandfather was born in 1862, he would have been ninety when I was born, maternal passed when I was 3, so. It's great that you have him for a resource and they have the greatest stories. I used to love talking with the one grandparent I had, my maternal grandmother who passed at 96, back in '78. Sniff...
Steve