Congratulations 1SG!!! I selfishly wish I could have stayed a 1SG forever. I think that 24-36 months in one position in one command, is optimal. While we aim to hold onto our leadership positions as long as can (or at least we should), there are reasons why our Army moves us out. Replacing leaders after their "time is up" allows for continued unit growth. Fresh eyes, ideas and blood allow leaders to take the guidon and the reigns of the unit and to continue to move it forward. If leaders stay "too long" in one position/unit, stagnation may occur and in some instances, comfort and complacency. No good comes from that.
Continuity in the unit is important when changing leaders out, but as long as we have developed, trained and prepared our junior leaders, a transition at the top should be a seamless transition. With that being said though, I am a fan of staggered changes at the 1SG and Company Command level as well as at the BN CSM and BN CDR level.
I've seen leaders who spent their leadership time all in the same battalion; that's a bad thing. There's a narrowing of horizons in the entire unit when your senior leadership has known each other since they were junior NCOs (HRC seems to force officers to PCS) and they all have dirt on each other.
The worst I've seen is five straight years of the same brigade CSM. Considering that the average assignment is four years or less for most people, this CSM ran the entire operation like a personal fiefdom. The brigade commander never disagreed with his senior enlisted advisor, mainly because he'd already survived three brigade commanders and knew everyone in the entire unit.
There's solid reasons for limiting command time and I strongly believe that anything over two years moves a unit away from the Army standard and toward that leader's individual standard.