I was told the the radio transmission signal strength was quite high on the pyronix detectors, hence why the batteries are still around the 2 year life, even though they are in sleep mode when system is unset, as opposed to risco's that only go sleep for 2 minutes.
I would of thought overall in the grand scheme of things, led's activating a couple of times a year on a two year life battery, wont make a noticable difference to battery life.