This is still bugging me. Every once in a while, I forget to zoom out and recording stops. I just played around with this, and it seems to have something to do with the length of the session. A new session seems to have a default length of 30 seconds, until you make it bigger by highlighting the multi-tack past the :30 mark, or record past the :30 mark outside of overdubbing.
My next question is: Can you set the length of the default session somewhere?