With AI2 this is not possible. In fact, I believe the Android SpeechRecognizer may have a built-in time out, so this is probably not an AI2 issue. Be aware, the AI2 Recognizer control is very basic. To control other features of the speech recognizer, you will have to use a different programming tool.
This quote, from Google says it all:
The implementation of this API is likely to stream audio to remote servers to perform speech recognition. As such this API is not intended to be used for continuous recognition, which would consume a significant amount of battery and bandwidth.
Regards,
Steve