Odds of Hanging On
Senator Daniel K. Inouye was the second-longest serving Senator in history, so the chances of retiring and gathering social security from a life in the Senate are slim.
On the other hand, 16 Senators have been promoted to President, so if you're truly ambitious, those are great odds.
The average tenure for a U.S. Senator is about two terms. That number has risen over time, perhaps because political life has a lot more appeal (good food in the cafeteria, free food and drinks at frequent cocktail parties). Another reason why term limits are becoming a hot topic.