We have a friend who, at the age of 98, was talking about going to college to learn about IT.
He celebrated his 100th birthday last November and is easily taken for someone in his mid 60s.
He's far more "with it" than people half his age, looks after himself (although his kids - all in their late 60s) visit regularly, does painting and decorating, programmes his VCRs and Freeview boxes (yes that is plural) and is, quite frankly, amazing.
He certainly has "all his marbles" in full action and would have had no problem in learning to use a computer if he had gone ahead.
It's no secret in the forums that I obtained a Mesh system nearly three years ago for an 81-year-old friend.
She took to it like a duck to water, updates all security aspects regularly, keeps up to date with friends and charity organisations' activities online and even got broadband six months before me because no one could get hold of her on the phone...:-)