Depending on your mounting system, the tailcap switch can be just as useful.
How/where do you plan on mounting your light and how do you grip your weapon?
Also, at what distance will you be shooting your firearms and still require white light? For anything 75 meters and below, 65 lumens is plenty. For 120, you won't notice much change in brightness at close ranges, but what you get is more "throw", meaning the light will reach out farther.
I've use a Surefire x200A on a 240B in a turret and it was plenty. Not ideal for a belt-fed, but you get my point.
A P61 bulb lasted over 4K rounds on my AR without a shock isolated bezel. I later added one anyway to prevent failure. Raith is right, though, it's cheaper to prevent the failure than to repair it. If it's for a firearm that your life will depend on, I'd say money is no object.