My Ls20 wouldnt come on high today. I was using a SF primary. My ZTS wouldnt even try to test it, this batt was dead. So, I put the batt back in, turned it on low, and started my stopwatch... :o
The nichias went for 2:40 (two hours, forty minutes!) :twothumbs
Keep in mind, I have no idea how long the battery was too dead before that to light the high beam, I mainly use the low on my LS. ;)
After that it went off pretty quick with a 3 minute moon mode, like tritium bright.
So dont feel like you have to carry a back up batt (Primary) for EDC use, once your high (far) beam goes, you have a while....