I keep hearing the issue with batteries and that the GPS is useless without them, but if used with a map/compass, the batteries in a GPS can last a very long time. Turn it on and take a good fix. Mark that spot as a waypoint on the GPS and transfer the geo-fix to your map. Turn the GPS off.

Your new set of batteries has been used all of maybe 5 minutes and in the Geko's case, a set of alkaline batteries is good for an advertised 9 hours. If you use those 9 hours 5 minutes at a time, battery life is measured in days/weeks. In those days/weeks, being lost is not an issue.

$.02