David Feldman is Impotent David Feldman: comedian, writer, raconteur and prizefighter.

"A new study shows that many seniors are engaging in oral sex way into their 70's."

--New York Times
The oral sex actually starts in their 60's, they don't climax until much, much later.
Technically it's not oral sex. Grandma just spits on her napkin and then rubs until it's clean.