Yes, it would definitely depend on your usage patterns as to which is "too expensive" - disposable primary cells or rechargeable LiIon's. My EDC light gets used several times every day and I would be replacing disposable cells every week or even more frequently. So that one gets rechargeables. The light on my shotgun, in contrast, rarely gets used and it still has the same pair of CR123 primaries in it as the day I installed the light - several years ago. I check that light by inspecting the batteries and turning it on for a few seconds every month or so, and as best I can guess, that initial pair of CR123's would probably last for the rest of my life, although I will no doubt replace the batteries within 5-10 years "just to be sure".