Interesting point about the rechargeables. For someone where this is their only light, buying 18650s and chargers really doesn't make sense, it will probably amount to a push after many years of use, and often using primaries is more convenient than remembering to recharge, although always starting with a charge topped off is nice.
For incandescent applications however, which in my case can draw between 3x and 20x as much power as any Fenix light, rechargeable is the only way to go. For example, my second most used light is a 1x18650 incan. A comparable 6p would drain 2CR123s an hour. My 2 AW C's used in my ROP-Hi (my third most used light), have MORE than paid for themselves compared to, say, a 3s2p CR123 configuration, like the Surefire M6, where you can blow over $30 an hour in CR123s.
The reason that I personally only go for LED lights now that accept 18650s (excluding keychain lights) has to do with the fact I already have a lot of 18650s, and want to standardize everything. A few times I've gone camping etc. and brought several lights that ALL use 18650s. Then, I bring a whole bunch of 18650s as spares as a way of standardizing.
