My wife, at 77yo, rides short rides with me. I greatly enjoy getting out with her. Often I will go on for a longer ride and she will return home.
Neighbors across the street are in early 70's/late 60's. She has extreme rheumatoid arthritis, but manages to ride a full step-through a mile or so with her husband. It is a great exercise for her. He rides about 6 miles or so, and considers that the ultimate in aerobics - "all one needs"!
Other neighbors across the street - mid 60's for him, late 50's for her, ride together.