Guys, good news! 

Robert, 85, married Maria, a lovely 25 year-old . . .

Since her new husband is so old, Maria decides that after their wedding, she and Robert should have   separate bedrooms, because she is concerned that her new but aged husband may over-exert himself if they spend the entire night together.

After the wedding festivities, Maria prepares herself for bed and the expected knock on the door.

Sure enough the knock comes, the door opens and there is Robert, her 85 year-old groom, ready for action. They unite as one. All goes well, Robert takes leave of his bride, and she prepares to go to sleep.

After a few minutes, Maria hears another knock on her bedroom door, and it's Robert. Again he is ready for more 'action'.

Somewhat surprised, Maria consents for more coupling. When the newly weds are done, Robert kisses his bride, bids her a fond good night and leaves.

She is set to go to sleep again, but, aha, you guessed it, Robert is back again, rapping on the door and is as fresh as a 25 year-old, ready for more 'action'. And, once more they enjoyed each other.

But as Robert 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, Robert.'

Robert, somewhat embarrassed, turns to Maria 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.