I had the same problems on each new camera that I bought, Leica, Hasselblad, and so on.
But the other or newer battery used on it have other duration: is it that the original one are not a good quality.? is it that we use more the camera to see though the viewfinder and the meter.? and this one use a lot of current.
The problem I had with all my M6, when I travel, is that I don't switsch off the camera, when I put it in my bag, because if I need it I will need the meter too, so it is always on. But in the bag it is not your finger that uses the meter, it depends about what we have very close of the shutter button. And very often I have to change the batteries, only for this reason.
Maybe some one other have more details with the M7, but we know that we depend of batteries, and on the M7 more than with other M.
Moral: always have batteries with us, like films.