Make it light as possible and 5.56. Don't use optics that need a battery.
Aimpoints can be left on for years without a battery change. To be super safe, just change it for a fresh one every January 1st (You can also store a spare battery in the battery cap). Much better quick sighting mechanism than standard aperture sights, and an AR equipped with one can be dropped from a chopper and still work fine, with no POI change. Nothing wrong with sticking to the standard sights, though. With practice, they can be quickly deployed to great effect. Just not as good as an Aimpoint red dot.
