That's funny. I went into the ANG in 1980 as a 29-year-old AF E-4. (E-4's were called "Sergeants" back then). Then after 4-long years I finally made E-5 S/Sgt. Promotions were so slow I figured I'd be forty before I ever got E-6. Never made it. I got out after six years, still an E-5.
At least I tried.
The other side of the coin today is I know of whole ANG units where you can make E-6 in less than 8 years with some units in 6.
I assure you, they didn't try.