Just a brief adendum regarding what I found as relative life expectancies beween 2 S76 batteries and a single DL 1/3n. My experience was based on use in a Nikon F2s Photomic, which used 2 rather bright LEDs for metering. The lithium battery gave about 20 minutes of metering, the silver oxides gave about 1/2 hour of meter on time. I have not bothered to do any sort of testing since, so my information should be considered quite dated.
William Robb