I used my V3i for 7.5 hours yesterday. I only ground balanced it one time, when I first started detecting-auto ground tracking speed 29, no offset. I hunted around in a 17 acre field. I noticed the tracking arrows appearing every now and then. I made frequent changes to either my filter, rx gain, or recovery delay on the fly several times and would stop walking and continue to sweep. I would see the tracking arrows appear for 2-4 short sweeps and go away. I even checked my ground balance every so often. Over clean ground, raised coil, pulled pinpoint button and lowered coil slowly and raised coil slowly and no static or noise. It seemed my ground balance was spot on. Something else too. I took four short breaks. I would turn the V3i off. Walk back to the truck come back and turn V3i on and start sweeping and no tracking arrows. Seemed machine retained its ground balance during power down and power up. I think the auto tracking system is dynamite. And I've seen some say the ground balance drifts in auto and they prefer lock trac. How would one ever know this? And isn't basically the same circuitry employed when using autotrack vs locktrac aside from lock trac not being updated with ground sensing changes? And this field had plenty of iron and nails too.