RE: No fancy battery cycler
John is right on the money. You don't want to just leave it on to run down the batteries. One big reason for this is that when a battery cell depletes down to empty, or near empty, it is at risk of going in to cell reversal. When this happens the cell is shot and is no good any longer. But the real risk of this is that you may not know the cell is bad until it's too late. A pack with a bad cell will appear to recharge as normal, and may appear to be fully charged. But when it's put into use that bad cell will cause the pack to fail, and more than likely resulting in the loss of the plane.
If you want to cycle the batteries please purchase a battery cycler. However, you can get along without one just fine. With the state of battery chemistry today packs do not need to be cycled in order to be maintained, and they do not develop "memory". The biggest reason you need a cycler for is to monitor the health of a battery pack. When a pack is new you can check the capacity of the pack. Then periodically as you use the pack it should be cycled to check it's capacity. When that capacity drops to approximately 80% of the initial capacity the pack should be taken out of use and be replaced.
Ken