The young fellow is about to marry and asks his grandfather how often a married couple should have sex.
His grandfather tells him, "When you first get married, you want it all the time, maybe several times a day; later on, maybe once a week. As you get older, you have sex maybe once a month. When you get really old, you are lucky to have it once a year -- maybe on your anniversary."
The young fellow asks, "How about you and Grandma?"
His grandfather replies, "Oh, we just have oral sex now. She goes into her bedroom and I go into my bedroom. She yells, 'F**k you,' and I holler back, 'F**k you, too!'"