What was the most amount of years you've seen someone transition to warrant from being an NCO? Particularly to a 255?

I knew an LTC with 28 years of service that went warrant because he didn't want to retire.

I did not know the amount of years but when I went through as a SFC; I had three MSGs in my class. Never too late. Just got to submit the Time in Service memo.

I had 12 years before I became a 255A.