This post has become obsolete as it was incorporated in the Spreading factor (SF), Time on Air and (Adaptive) Data Rate
To save battery devices should minimize used spreading factor, and therefore time-on-air (ToA). When a LoRa device has ADR enabled, the network measures signal strength and replies to the device what SF to use from now on. LoRa devices can be set ADR ON or OFF. Switching ADR OFF is only advised for continually moving objects.
Apart from battery considerations, added advantage of ADR is the increased network capacity: when a specific spot has many LoRa devices sending at a high SF is fitted with an extra gateway, that gateway can reroute the traffic and drastically decrease ToA of the devices around the gateway.