Here's the info from eo-tech.
http://www.eotechinc.com/dear-valued-eotech-customer

as for batteries not lasting, my T2 will last for 5 years when always left on. That said, my last Eo-Tech 512 lasted the spec'd time they stated. (but I forget how long that was, did a test here on the fire a few years ago). Bottom line, battery life is not a problem on newer models.

I bought a new sideways battery model and figured it was about perfect until it started going off when I shot the gun. I sold everything eo-tech and went Aimpoint.