“I made SGT E-5 in 2-1/2 years in the U.S. Army. I’m not sure how fast promotions come in the Air Force, but I assume it’s similar to the army.”
No, they weren’t so fast when I was in (1970 - 1974). The norm was E-4 in about two years, but E-5 in four was rare, and most E-4s got their fourth stripe (E-5 Staff Sergeant) after they re-upped.