I was wondering about that. One year I borrowed one and got the long life lithium. Stopped at a campsite for a late lunch, decided to stay, no evening paddle, flipped the canoe over for the night.

Next morning the batteries were dead. I assume I left it on but I do remember it had a light and I think that was off so I don't know if the light had anything to do with it or if ~15 hours of pinging the moon on auto depth sucks more juice.

Last trip I used a different one and easily used it 15 hours the last two days of an 11 day trip. I'll take a wild guess and say I had it on for ~50 hours that trip. Same set of the lithium whatevers was still showing over 12 volts in 199 feet of water on my way out as I recall.