I would say that it might be both. It is a blessing as most have grand kids that they can enjoy. Stories that they can tell of the past when they were growing up. They can teach other folks what all they have learned.
Then the down side of it would have to be the fact that you are not as strong as you once were. Your memory is not what it once was.
As far as sickness goes, that can strike at any age really. Any sickness, no matter what it is, can strike you even at a very young age including a new born.
The one thing that I have learned from both of my parents is, never put off tomorrow what you can do today as you never know if you will be able to do it tomorrow or not. I think I am about the worst on putting stuff of until tomorrow. Most of which I regret putting off.