I didn't used to think so, and that is should be left up to the voters. But, the incumbent position is such a powerful one and it quickly becomes a thinking of only they can do the job -- both in their mind and the voters. And that's nonsense of course. History is littered with folk who stayed way too long. Joe Biden is one. Others include FDR, Winston Churchill and possibly both Queens Elizabeth (later one for sure). Mine you Vladimir Horowitz and Eubie Blake gave a couple of decent perfomances in their 90's.

Nancy Pelosi? she has achieved a lot and certainly can afford to retire.