The 10X's I have also seem to hold charge longer than I would expect...
A note on the rational behind not use rechargeables for Tactical Lights:
1) Before SureFire took it upon themselves to purchase millions of American-made batteries and have them SureFire labelled, and offer them at cost to the end-user [NB: the reason why SureFire had to increase the price they were charging was because transportation and packaging costs increased]
Before SureFire were the first company to offer high quality CR123A batteries at low cost, one had to purchase the batteries from the likes of Duracell or Energiser at prices they still charge (and worse) in retail stores.
Once other brands got in on the game and started offering non-American made batteries - the market was flooded by cheap (and dangerous in numerous cases) Chinese-made CR123A batteries.
2) Before LED lights it was normal that a flashlight could not be powered by either primary or rechargeable batteries. Also, the NiCad and NiMH batteries were not as high quality.
Now in the world of LED flashlights that can accept a variety of power sources, and the high capacity, high current draw capable LiIon rechargeable batteries the situation is somewhat different.
3) In the world where SureFire's primary markets operate it is not often feasible or practicable for users to be slaved to a battery charger. Relying on rechargeable batteries rather than primary SF123A batteries can result in your lights being dead when you need them.
I honestly believe SureFire are not in business to sell batteries, or to make money from their SF123A batteries. The attitude of SureFire employees I know is that SureFire offer their SF123A batteries is a service to their users so that the users can get the best from the products they have invested in and rely on.
If one uses a flashlight a lot, and has reliable access to a battery charger or other suitable arrangement then I see no reason why rechargeable batteries should not be used where it is safe to do so.
However, for "tactical" use I believe one should use dedicated lights designed and intended for the specific 'tactical application' being performed. This situation is not, in my opinion a suitable time to cut corners to save a couple bucks. BTW, I've been of the same opinion even when the £ wasn't nearly as strong against the $.