To answer the other part of your question - if you use the default for the second parameter you will get an execution with each frame, no matter what the frame rate is, which as Jeff said is the fastest you can get from this command:
Code:
viz.starttimer(0, numRepeats = viz.FOREVER)
or
viz.starttimer(0, viz.FASTEST_EXPIRATION, viz.FOREVER)
Best Regards,
Walter