As someone who was commissioned in 1982, I can tell you what should be expected for my year group and if he was commissioned during the same time frame you can extrapolate from there. Mind you, the promotion rates were faster during the Viet Nam era, but once that conflict/police action/war was over, there was a huge reduction in force (RIF).
For my year group, the majority that are still in are Lieutenant Colonels (LTC) with some of the golden children being Colonels also known as full bird Colonels. Chances are your friend was passed over for LTC. I'm willing to bet he didn't get picked up for the Command and General Staff College (CGSC) which more often than not is a career killer, although some do make it to LTC without it.
The Army has an up or out policy. So after getting passed over so many times for promotion, you are forced to leave. I do think that once someone makes it to LTC, they can stick around for 30 years, but don't hold me to that one.
It doesn't mean he was a toad. You only have to piss off one guy and your career is pretty much toast.
Do you know what his branch was, i.e, Infantry, Armor, Field Artillery, etc.?
I hope this helps.