I have had the Geotagger N2 for a couple of years and have used it with the D300 and now the D800. I never use Auto. I always just turn it on and leave it on. I've never had any camera battery issues, even when leaving the GPS on all day. The reason I do that is to keep the GPS location synced all the time. The startup time is short, but still finite and I want to be able to turn the camera on and take a picture immediately without any delay in the GPS catching up to my location. I always start the day with a charged N2 and good camera batteries for best results. Personal preference, but it works for me.