![Image](https://forums.factorio.com/images/ext/e7f806a4534f7020e3acc8f60c0ed22e.jpg)
As can be seen in the above screenshot, inserters ready to load into a train go inactive when there isn't a train present. Depleted miners go into inactive state. However the mining drills (that still have ore) that are ready to direct-load into the train do not go inactive when there is no train present. Seems like this is a potential UPS drain that could get the same optimization as the inserters for this case.