Scenario speed

There is no maximum. If you put the speed slider to its highest setting, the scenario will run as fast as your computer can run it.

Okay. Is there any way of finding out how many times the act() method is called per second?

You can measure it. Use System.currentTimeMillis() to count passing time, and count the number of act cycles until one second is up. Why do you want to do this?

I want to make things happen for a specific number of seconds, instead of a arbitrary number of act cycles. I'll use System.currentTimeMillis().