At 85 years of age, Roger married Jenny, a lovely 25 year old.

Since her new husband is so old, Jenny decides that after their
wedding she and Roger should have separate bedrooms, because she is
concerned that her new but aged husband may overexert himself if they
spend the entire night together.
After the wedding festivities Jenny prepares herself for bed and
the expected knock' on the door. Sure enough the knock comes, the door opens
and there is Roger, her 85 year old groom, ready for action.

They unite as one.

All goes well, Roger takes leave of his bride, and she prepares
to go to sleep. After a few minutes, Jenny hears another knock on her
bedroom door, and it's Roger. Again he is ready for more 'action'.

Somewhat surprised, Jenny consents for more coupling. When the
newly weds are done, Roger kisses his bride, bids her a fond good night and
leaves. She is set to go to sleep again, but, aha you guessed it - Roger
Is back again, rapping on the door, and is as fresh as a 25-year-old,
ready for more 'action'.

And, once more they enjoy each other. But as Roger gets set to
leave again, his young bride says to him, 'I am thoroughly impressed that at
your age you can perform so well and so often. I have been with guys
less than a third of your age who were only good once. You are truly
a great lover, Roger.'

Roger, somewhat embarrassed, turns to Jenny and says: 'You mean
I was here already?'

The moral of the story: Don't be afraid of getting old,
Alzheimer's has its advantages.