I'm aware of this, but in my own experience, I'm not sure it's really something to worry about in this particular case. And I'm talking about regular AA NiMH that you might buy at the supermarket, not something like more exotic rechargeable Li-ion batteries, which I would be very careful with in terms of charging or deeply discharging.

I use some Engergizer AA NiMH in a weather radio that is always on in stand-by mode. I continually let the batteries drain until the radio dies, swap with an already charged pair, and then put the depleted cells in the mini-recharger that it came with. I repeat this cycle about twice a week and I've been doing this for a couple years on the same set of batteries and have not noticed any appreciable decrease in runtime compared to when the batteries were new. Of course, maybe the radio doesn't discharge the batteries quite as low as some energy-sipping LED flashlight might, so maybe it's not a good comparison. The kids could get incandescent flashlights, which will still drain the batteries, but probably not down as low as an LED would.

In any case, while I would generally want to heed the advice that the longevity of NiMH batteries is related to the depth of discharge, I'm not sure I would worry about it with the kiddies' flashlights. In fact, I would think that they would grow bored with wanting to play with flashlights every night before the first set of rechargeable batteries eventually wore out. <img src="/images/graemlins/smile.gif" alt="" />