When someone is living an extravegant life full of on-the-edge experiences and partying. These people are usually very popular and party alot.
"Damn. Joe is living a primed life. He parties with Playboy Bunnies everynight."
"and he lives in a penthouse in beverly hills."
Prime of life is the mature adulthood, perhaps between 35 and 45.
Astronauts are usually chosen from people who are in the prime of life.