Bernie and Biden
I like Joe Biden a lot, and think that Bernie Sanders has done a good job shaking up some of the settled wisdom of the Democratic party, but they are too damn old to be President. So is Trump, so was Reagan in his second term, and, for that matter, so was Hillary. I think that it's crazy to elect anybody over 65 as President, and somebody in their mid forties through fifties should be ideal.
I also think judges should face retirement at 70 or 72, and Senators and Congressmen at 75.