There are lights that are comparable in max output, but not with AA batteries. All the others pretty much use Lithium primaries or Li-ion rechargeables.
As has been pointed out elsewhere, the parastic drain is very slow. I think it would take longer than a year to typically drain a fresh set of batteries below what you would notice.
I initially always kept my TK40 on lockout when not in use, but for the last 2 months I haven't bothered. I generally uses it several times a week for about 10-15 minutes at a time (walk the dog, etc.
I have it loaded with 8 eneloops, and have not noticed any loss of output or power yet after these two months of intermittent use and no lockout. It is getting to the point where it would probably need a recharge anyway, just based on usage (generally would go about 2 hours continuous use on 8 2000 mAh eneloops on turbo)
If I were not going to use it for a few months I would certainly put it on lockout. BTW, I found that if I bend the 4 gold springs at the bezel end of the battery carrier down a couple MM it allows me to lock out the light with about 1 turn, and does not affect the performance of the light in any other way.
There are several other good choices available for lights that have similar output; I'm finding that I like my Olight M30 quite a bit for its smaller form factor and interface, and my DBS V3 MC-E for its throwy flood. If you like having the 8 modes on the TK40, however, you won't find that in comparable lights - most have simpler interfaces, with low-high, low-med-high or sometimes low-med-high-strobe. On the other hand many would argue that SOS and beacon/slow flash are useless anyhow; many also don't like strobe.
I'm planning to do a comparison review/beamshot shootout between the Legion II, Fenix TK40, EagleTac M2CX, DBS MC-E, Olight M30 Triton, Epsilon ED-P72, Ultrafire RL-2088, Jetbeam M1X, and Solar Force L1000 P7. I have all the other lights, I am just waiting on the Legion II to do the review. These all put out lots of light on max, but also have a lot of differences.
I also have an XTAR howitzer on order; it will be interesting to compare its beam to these other "big guns".