This is a trend that has been developing in the last 20 years and accelerated by the ability of EP Sailors to take the advancement exam early - a late 90s/early 2000s development. We have to be very careful about putting our people - rock stars though they may be - in positions of leadership, without a solid foundation of maturity and experience that comes with time in service. Obviously, there's a balance to be struck here, but most of us have seen the young CPO who struggles in this way - lacking credibility within the Goat Locker, or legitimacy on the deck plates because they're so young...
I work with a lot of early Chiefs and I don't think age is the issue per se. We have officers in their 20s with more responsibility than Chiefs. In fact the most immature Chief I've worked with was a guy in his 30s ultimately removed from the boat for DUI x3, and another 35 year old who decided it would be a fun idea to horse around with an E-5 by whipping him with his belt in front of the squadron staff during an inspection assist. The younger Chiefs still want to make senior Chief or LDO, or at a very least have more than 10 years until retirement, and don't want to screw it up.
The two issues I have with early Chiefs are:
1) They are often 'soft' in the leadership category, particularly when it comes to disciplining sailors, because they rose through the ranks mostly by being awarded auto E-4 for nuke (auto E-5 with a STAR re-enlistment), and then being very good at taking a couple of written exams.
2) You look toward the Chief as the guy who knows how to fix the division's gear and make sure everyone does it right. A 7 year Chief sometimes isn't that guy, especially if he has only seen one other boat that didn't have the same equipment.
If I had my way I'd take away the automatic advancement in rate for nukes and roll the difference in pay to special pay, that way you don't get an E-5 (sometimes E-6) showing up to his first sea command. I only have one data point for a non nuke hot runner who made senior Chief in about 10 years. He was on top of the game and had no issues with getting credibility with the men.