Note that EVFs use more batteries than rear LCDs. It probably relates to the resolution and updated frequency of the display.I can only speak empirically to battery life on the 907x/CFV-100c, as I'm not into formal camera testing. But I've shot pretty much every day with it and all I can say is that considering its "viewfinder" is a good-sized LCD screen the battery life seems terrific. It seems quite efficient. I'm glad I bought a spare battery when I ordered the camera and back, but I've taken to leaving it at home on most of my mini adventures.
That said, the context for me is pretty selective shooting. I shoot digital with essentially the same tempo I shot (shoot) film. And slower still with medium format.