How often do you change the battery in your ARC?

Let me change that to how often do you NEED TO change the battery in your ARC? I was just wondering how much usage you get out of the 6 or so hrs of light in real time. In particular I was wondering about a keychain mounted scenario.

I only change the batteries in my keychain Photon 2 once or twice a year. When it gets dimmer than an infinity. Thats probably only 2 hrs of actual runtime.

My lanyard mounted Arc sees less intermittent use but more prolonged use on camping trips and such. I will generally put a new battery before each trip. Not that it needs it or anything, I just like to know I have light in reserve if an emergency should arise.

I usually change my Arc AAA batteries about every three to four months. (The most heavily used lights) The others, maybe every 6 months or so...

So far, it looks like the "AAA" battery lasts about 4 months and the LS2 blem goes for about a month and a half. I am not sure if this is representative of anybody elses use pattern or not. I have been using both lights basically every day.

My LS2 using NiMH AAs - every 3 days - if hiking then more often