when my dad "retired" - actually was made redundent - in his late 50's, he worked for a few years as a security gaurd to save some money (he walked away from the family with nothign but the clothes off his back), saved enough to buy an old wreck of a house and refurbished it and sold it, bought another, etc., now for 30 years. he is still working on a huge old wreck of a building, living in it and renting off a few rooms while fixing the rest of it, and he is mentally clear and relativly healthy.
my mother, when she was 65, retired, and made it clear she wasn't going to volenteer or take any classes, because she felt that she had worked hard enough. 20 years later, she can't remember what day it is, she is horribly sick, and misrable.
having something to do is key to living a long and happy life.