E6 in 3 years? Is there such thing as making rank too soon?

In SF this is easy to do. E-7 in 7 years.

I think so for at least 90% of the cases. Back in the early 90s it took me a little under 6 years to make E5 (too long) in BRAGG, where a lot others were in the same boat. However, once I PCS'd to Germany I ran into several fast trackers making E5 in 2 to 3 years. First impression: this is nuts. They don't know sh*t and don't have the experience. I ran laps around these guys. So after a while I reevaluated them but I still thought the same. I respected them tho and soon enough I went to the E5 board and got promoted. But as E5 I was outdoing those E5'a and other E6's so I got sent to the E6 board and not long after got E6 and E7 back in the states. Some said E7 in 11 years was too fast (in general) but I was mentally ready and was very cool under stress and made good decisions so I did great. I think your maturity (both personal and professional) and experiences gained is what matters most.

It all depends really on the individual. A great leader is a great leader regardless of experience level. Some folks are great right out of the box. Most of us have to work harder to get there.

A categorical and rotund YES! I know people say "It depends on the person" and things like that. I could apply that to myself - not that I had get promoted that fast, quite the opposite - but when I joined the Army I was a very mature young person. I could have got promoted to E-5, E-6, and I was the responsible Christian guy, church goer, husband, blah, blah, you get the picture. I saw lots of people with the right schools, experience, and even personality become crappy leaders. I figured the "secret ingredient": Time. To be a "seasoned" service member you have to have time. It is the thing that give empathy for the newly married Soldier, or makes you give a 2nd chance to that screw up private or even NCO. According to the Nieves Psychological Research Institute - read "my personal opinion" - when we are young we have less tolerance than when we are older. We also rely more on thinking processes combined with experience and seasoned with instinct than by-the-book reflexes or "this is how I get things done" primal instincts, for those who act on impulse or feelings.
It took me 11 years to make E-5, six more to make E-6, but the moment I became an NCO, Soldiers were instantly attracted to me as they saw me, I believe, as some sort of "elder" or father figure.
In short, "seasoning" or "aging" process is vital to the [good] quality of any leader, in my opinion.

I made Sgt in 2 years and SSgt in 5 years in the Marine Corps. I had no problems.

That is a difficult call. Some individuals are able to handle quick climbs up the ladder, others peak out and are not productive. I was one of those (in my enlisted days) that automatically was promoted to E4 on completion of my first year because of the school I was in. Then transferred to a remote assignment where E5 was automatic after 8 months. In the old days, they had what was called "Blood Stripes." (Maybe still do). A colonel or higher commander would keep enlisted ranks E6 and below in the command. If a staff sergeant was reduced in rank, the command would hold a board and select a qualified E5 to receive stripe. I was fortunate in that I was selected and made E6 in less than 3 years. Then the Army changed the rules and you had to have a certain number of TIS to be promoted. I languished at E6 for several years, while individuals promoted to E6 after me were promoted to E7. Solved the problem by getting my commission. Guess the bottom line is, I don't like cookie cutter promotions (so many years in service, promotions come) but sometimes rank can come too fast. A lot of it depends on the maturity of the individual

Would have to be a real water-walker. Problem would be living up to the expectations and the responsibility placed on an E6. Best leave some time for seasoning.

I think that there is a big difference in leadership experience and technical capabilities. There are some technical MOS's that make it very easy to get promoted to E-7 quickly however, the Combat Arms professions in the Army provide the easiest route. There are just a significant amount of billets to be filled. Personally, I was selected for SFC (E-7) in 9 years and I found myself drinking from a fire hose. It was extremely challenging but not impossible. I hit the books and operated as a sponge daily. Pick a few good mentors who you trust and get other Senior NCO's perspectives on your leadership. Many will be different so try to find that common thread between all of them and implement it. More often than not, I found myself questioning my ability and my decisions early on. Once I got comfortable with myself through experience things got easier. Remember to educate yourself and the experience will come.

In the Army, if you have a A.S. In Nursing & licensed in any state. You are automatically promoted to Sgt./E-5!! Yet if you are a BSN, you come in as a 0-1!! It’s screwed up system, because if an ASN, take the same friggen National exam as a BSN!! Thus, many times that the ASN has to orient these new grads!!! They should make ASN’s CWO’s. Or the military is going to lose every ASN who is generally “floor” proficient than the new BSN, not to be forced train them, unless they are Officers!!! I could tell you horribly true things that are swept rug, including the new MD’s, who would not even to the RN’s comments regarding a patient who had a simple surgery, yet 6 days after admission was dead

I went to Vietnam as a Grunt. Upon my return I branch transferred to Finance. I was working in Out-processing with 2nd Armored Division Finance, Ft Hood, TX, when who appears before me, one of the Grunts from my Infantry unit (C 3/21, 196th LIB). I was shocked to see that he had made E-6. He was a draftee and had almost a year's time in grade. Here he was out-processing and leaving the Army. A large part of our unit was KIA or WIA during Tet 68 (I left Dec 67, missed it by less than a month) and he found himself as platoon Sgt. He knew if he stayed in he was going back to RVN. He decided to git while the gittin' was good. I believe he earned it and it wasn't premature at the time.....