I'm with Carl on the various DX brands. Do yourself a favor and don't get something that is five mode. That means you have to scroll through High-medium-low-strobe-SOS everytime you want to turn it off. Two modes, High-Low are perfect. Lumens are all theoretical anyway, not what is actually coming out the front. You can spend three times as much for a really nice reflector and lens and might gain 100 lumens. The human eye can't really tell the difference between 900 and 1000 lumens anyway, so don't get caught up in that.
I believe Sanyo is also another high end 18650 brand to look at.
Because I'm on two volunteer fire departments and need two sets of gear, plus lights for the coyote gun, the light on the night stand, the light next to the front door, and the lights in each car, I have probably 15 18650s now. Most are 2400mah, a few are 3200-3400mah, and I carry spares where they're critical. My high end batteries are for my critical applications, like my fire gear, the rest, I go cheap.
The only pitfall I'll say about these cheaper lights is the switch. They're cheap and not momentary on. I've had two fail over the years, but after years of service. However, because they don't have a momentary on, they're not ideal for tactical stuff. You can click them on, then partially press in and they'll turn off until you release, but it's not ideal. If you're looking for a high end tactical light, look at Olight, JetBeam or Sunwayman. All three are great lights, a lot cheaper than the surefires and other name brands, but IMHO, they're not worth it for your purposes of field work.
Finally, a few years ago I was taking a tactical class and dropped my light. I went to pick it up when the instructor told me to engage the target that I was way too close to already. I realized I'd compromised my safety to pick up my $60 light. After the fact, I told myself if it was real world and I knew there was a threat, I'll buy another flashlight. I still carry a higher end light for edc, but after three years of service, if I lose it today, it's all good. For that reason, I think it's worth reminding yourself that anything you own should be disposable if retrieving it might put you in a bad position. A cheap light makes this decision a lot easier.
