You would be much better off with an AimPoint or EOtech. If you think about how you might use your rifle in a real defensive situation, a great many of them would involve you standing/laying in a dark area and shooting into a brighter one. The Reflex's reticle disappears in this situation, because the tritium isn't bright enough to light the reticle unless it is truly DARK, and the fiber optic collectors on the front won't collect enough light when you're in the shade. Plus, the lense is blue-tinted, which affects the way you see colors, and makes everything darker.
The battery issue, *especially* with the AimPoints, is really a non-issue. An AimPoint battery will give you at least 1,000-2,000 hours of realistic use, and when it finally begins to die, it will give you plenty of notice. Replacements are $5, and the lithium battery has a 10 year shelf-life, which is about the same lifespan of the tritium insert of the Reflex. Replacing that insert costs nearly the entire cost of the optic, BTW.
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-Troy