The batteries that come with my metal detector lasted for 18-20 hours and the indicator still showed full.
On my air and buried coin test garden, the metal detector can only detect about 4 inches and pushing it to 5 inches.
I have noticed that the arrangement for adjusting the coil to shank angle does not provide enough friction to prevent the weight of the coil from tilting the front of the coil down. This is negative feedback regarding the Search Coil Size and Shape feature of metal-detectors.