Switching Android SensorManager speed. What's a good practice?

Question

I'm interested to switch between different sensor orientation speeds over time to optimize the program ie.. battery life. The routine may be called very often. I'm looking for the right practice.

       sensorManager = (SensorManager)getSystemService(Context.SENSOR_SERVICE);
       sensorManager.registerListener(sensorListener, SensorManager.SENSOR_ORIENTATION, SensorManager.SENSOR_DELAY_FASTEST);
       //... 1) unregister then register new speed OR
       //... 2) register new speed without registering
       sensorManager.unregisterListener(sensorListener);

Should I unregister the listener and then register with SensorManager.SENSOR_DELAY_NORMAL
OR
Should I not bother unregistering the listener?

thanks.