What age you think the memory keeps fading and you just cannot recollect?

My memory is not so good as before when I was in my thirties. But my 81-year-old father remembers things well in his young days. My father has a poor memory about what is happening now. Sometimes when he talks to us, he is just repeating the same thing again and again, making us laugh, but we are still very patient to listen to him in order to make him happy. We don't get in his word, we only tell him that he has talked about it, yet he seems happy to go on with his topic. My old father is really interesting though. I feel happy with him though he is talkative. I love to hear his voice, my lovely father. The older he is, the more lovely he is. lol

To me the brain power's capacity doesn't usually follow the normal age factor. Health factor plays the most crutial part in determining a person's brain power. If a person's health is in the optimum, even though she is already 80 years old, she is able to think and remember everything as normal. I have a grandmother who has a very sharp memory and now she's over 80. She remembers everything I told her, and it was amazing.

I know a family friend who is a lawer who is now 93 years and recently he dictated a letter to me to be typed and he has 100% presence of mind and memory is as rich as any youngster. So I am not in a position to tell at what age the memory fades.