I'm going to start using an adjustable led RMR on my edc. I've read that keeping it on the #4 setting will yield a long battery life (4 years). I think leaving it on the automatic mode will give the best sight picture for any setting. I plan on changing the battery every year anyway. I will be indoors without a cover shirt most of the time and with one when outside. I wonder what the battery life will be on the auto setting? The brightness inside appears to be a six. Suggestions/opinions?