REFLEX ++ automatically adjusts the light to provide boosted output when riding hard and fast then intuitively dimming for the slower sections such as climbs. This is all to optimise battery capacity, to provide extra light when needed and save it when not required.
Reflex achieves this by using data from 3D digital accelerometers including gyroscope and thermistors. It continually analyses the data to make seamless adjustments to benefit the rider, probably better than the rider can. In reality it is a form of artificial intelligence. The selected run time will be achieved by averaging the output over the period.