Ed returns from the doctor and tells his wife that the doctor has told
him he has only 24 hours to live. Given this prognosis, Ed asks his
wife for sex.

Naturally, she agrees, and they make love.
About six hours later, the husband goes to his wife and says, "Honey,
you know I now have only 18 hours to live. Could we please do it one
more time?"

Of course, the wife agrees and they do it again.
Later, as the man gets into bed, he looks at his watch and realizes he
now has only 8 hours left. He touches his wife's shoulder and asks,
"Honey, please... Just one more time before I die ?"

She says, "Of course, dear." And they make love for the third time.
After this session, the wife rolls over & falls asleep.

Ed, however, worried about his impending death, tosses & turns until
he's down to 4 more hours.
He taps his wife, who rouses.

"Honey, I have only 4 more hours, do you think we could............."?
At this point the wife sits up and says,

"Listen Ed, I have to get up in the morning... You don't."