I was in 22 years, too and have to back you up on this. The Air Force intentionally slowed down promotions in the mid 70's and it was extremely difficult to make E-5 on your first enlistment. The average time in service for an E-5 was between 5-7 years. E-6 was about 14 years, depending on your job. Once I got past E-6 I made rank pretty quick.
Lots of folks didn't understand why promotions were slow in USAF. Simple attrition, or lack of, was the cause. A guy entering after WWII and making E-9 in 13-14 years would probably stay for a full career and retire near 30 years. That blocked promotion for those below him, and rippled down through the ranks. It took AF planners a long time to get our rank structure un-stuck and in line with other services.