There's a way to benchmark ET:
- open console (~)
/timedemo 1
/demo DEMONAME
When the demo is finished open console again.
There will be data about the FPS.
Min. FPS/Max FPS
Average, 99%, 99.9%.
The demo isn't running at normal speed. It's running faster. So you won't have to wait 20 to 30 minutes.
My guess the demo has to be in the /demo folder.