I screwed up my courage last week and asked Ernest about batteries for flash guns. Then I took his advice...and bought a set of the Toshiba AA cells for a weekend shoot. $ 4.80.
The advice proved good. I used the 4 cells in a Fujifilm EF 42 flash with my Fujifilm X-Pro1 and an 18mm lens. I set the ISO to 320 and wandered around Big Al's Poker Run car show for 4 hours. The camera was set to do forced flash - it fired every time - frequently on +1 or +1.5 flash boost due to the nature of the harsh light contrast.
Over 280 shots on the day. I should have expected 120-140 from the set of batteries. But there is the 280 on the card and in my hard drive.
Whether this is due to the sterling nature of Japanese electricity or the Fujifilm flash is remarkably economical, I don't know - but this sort of performance means that I'll be using the combination in the future. I can't remember getting anywhere near this level of performance with alkaline Duracell or Eveready in the past.