Used to be about 7-8 years to hit GEO1A3 (GEO5), then another 5-10 years to hit the salary ceiling.

If you joined in 2015 or later, though, you could take up to 10-15 years to hit GEO5 if you don't take on any higher appointment. This is based on the observation that there are still many ~10 YOE folks who are currently stuck at GEO4. As for how long it takes to hit the 5 or 5A ceiling, it's hard to tell right now because the slowed down promotion rates and drastically reduced MIs have not been in effect for long enough. MIs become smaller and smaller the closer you are to the ceiling.