The decline of one's mental abilities is a given as one grows older...regardless of who you are. The thing is it will vary for each individual...some very early, while other much later...and is dependant on a great many factors...including mental activeness.
Getting older but my grade keeps going up

Yes, also someone who wasn't good at chess when they were younger could probably get better as they get older simply because they didn't know much to begin with. Would probably get tired faster, though (as another poster pointed out)

cwwiss said: "But I digress.. There are still lots of top players stricken in years but the World champion is always below 50, in recent years at least."
I think age is a very minor factor in performance. It probably "shifts the bell curve" slightly to the left. What this means is that for the vast majority of people, unless they suffer significant personal cognitive decline, their performance will mostly be determined by the usual factors -- training, study, experience, etc. Some of these (judgment) may improve with age. Mathematicians experience a similar phenomenon -- younger mathematicians contribute "trail-blazing" (new ideas, "outside-the-box" thinking) while older mathematicians excel at consolidation of old ideas, seeing the big picture, problems where judgment and experience are more important than trail-blazing insight.
As far as world champions go, the reason recent ones have been younger than 50 probably stems from two facts: world class competitive chess has become a high-stakes profession the past 50-75 years, and in order to perform at that level, you need to be many standard deviations to the right on the bell curve. If the bell curve is moved even slightly to the left, no matter how many standard deviations you go to the right, you won't be able to compete against a younger player whose bell curve is slightly to the right. (If that makes sense.)

Why should you expect your grade to go down just because you get older? If a person continues to work seriously on their chess, they should be able to improve no matter what their age.
Think about it. Older (or younger!) players whose ratings go down do so because they aren't working hard enough on improving their game.
The age thing in chess is WAY overblown.

nice to hear that andre harding because i am too is growing older im 57 and i want to meet my limits.

Annabella you look gorgeous. Why are women chess players hot but guy's not?
Speak for yourself.
Ha! Yes, you are gorgeous as well Scott ;)

No doubt one day i'll be to tired to study anymore because of old age.Which, i'm guessing, will be the time when my grade will start to go down.
I won a major title two years ago for the first time and my ambition is to win an Open section.But the years are starting to add up.I just hope I haven't left it to late.
Annabella you look gorgeous. Why are women chess players hot but guy's not?
Speak for yourself.
Someone's on an ego trip lol. Beauty's in the eye of the beholder not the beheld