Primary Lithiums are excellent but they are expensive. I have had good results using Soshine RCR123s 3.7V rechargables.



http://www.dealextreme.com/details.dx/sku.13811 (these are even cheaper than any primary CR123s available for retail in the majority of retail outlets in the UK)

In the UK a single CR123A can cost up to $8 each from well known supermarket outlets. I do keep a small supply of primary CR123A (around a dozen or so) for their long term storage ability but now mainly use rechargeable cells instead for everyday use.

Fenix T1, High 225 lux: 1.0 hrs, 2 Soshine RCR123 ==> $0.04/hr (assuming 200 recharges)