Long Runtime / Rechargable LED Question

I'm looking for another light for nighttime hiking to compliment my L2 (It gets expensive having to constantly get new batteries for it!). I'd like to find something that runs on rechargable CR123A batteries (whatever the rechargable versions are called... pilas?). I'd like to have a decent amount of output for walking on trails at night, but runtime is also very important. Ideally, I'd like it to find a Surefire that can do this, just because I love the brand and trust it more than any others, but I'm open to other suggestions as well. Also, I have a couple of questions about these rechargable batteries too... first, how long do they typically last, and second, is there a downside of recharging a battery that isn't completely empty? Do I have to let them rundown before recharging them, or can I just toss some 80% batteries on the charge and not cause any damage to them?

Thanks for any replies.

I believe the problem you are refering to is "memory" and if I remember correctly that primarily happens with NiCad batteriers, but if you use a Lithium-Ion rechargable, you can recharge at any level of capacity with no ill effects.

A headlamp works pretty good for hiking. The 5mm LED kind is plenty bright and lasts a long time. They tend to use AA or AAA, and not the cell you are looking for though.