That dog sure can rip!
How often does it have to wait for you to catch up on rides?
I have trained her to run behind me. That only works if I'm riding alone, or first in a group though. We rode Bear Mountain DH with Rewoga and Brace…Rewoga started first and sasha tore off after him barking like crazy. I left about ten seconds later and she kept running back to me barking at me as if to say "hurry up! He's beating you!" then running to catch up to Rewoga again.
To answer Matt's question, she has no problem doing a full lap without stopping. She could probably go faster if I wasn't in the way.