I'm pretty sure that if I'm going to spend time thinking about Constitutional changes that aren't going to happen I'd rather think about term limits for the Supremes than about changing the 14th Amendment, so I'll send you here for the other constitutional hocus-pocus and go another round on SCOTUS, as John Sides (cautious and probably anti) and Matt Yglesias (pro) both have added thoughtful posts today that I recommend.
I'm not really changing my position overall (cautious, but interested), but I do think I've fallen into one trap, which is that I previously said that I didn't like the pressure in the current system to go as young as possible. As I think about it, however, I'm not at all against young Supreme Court Justices. Why shouldn't we have Justices in their 40s -- or in their 30s? Sides (who points out that nominees have not, in fact, been getting younger) says that "It’s hard for potential nominees to be seen as sufficiently qualified for the Court" unless they're at least around 50, but why is that? After all, James Madison (warning: glib oversimplification!) wrote the Constitution when was not yet 40 (b. 1751), so should it really be impossible to imagine someone in her 30s interpreting it?
What I'm actually not thrilled with is the idea that one of the three co-equal branches of government is restricted in practical terms to a narrow meritocratic group of those who go to one of a handful of law schools and then groom themselves for the job by both convincing their co-partisans that they are safe votes and by never saying or writing anything controversial. But, no, I'm not really against young Justices at all.
Indeed, I'll note that the Framers didn't include any age threshold for serving on the bench. I think they were correct. Moreover, as long as we're talking Constitutional changes that aren't going to happen, I'd probably go ahead and follow John Seery's suggestion to eliminate minimum ages for Congress and the Presidency. And lower the voting age to, oh, 12, something around there (that last one doesn't require an Amendment; states are free to lower their voting ages right now, if they want).