Continuous speech input mode always ends after 20 seconds of silence

Hello,

In Google's Web Speech API Demonstration[1] and in my application,
continuous speech input always ends after 20 seconds of microphone silence.
Do you have any ideas for how to get around this?

Is creating an external speech service a potential option?

Warm wishes,
Daniel

[1] http://www.google.com/intl/en/chrome/demos/speech.html