If you use SR41 (silver oxide variant), you'll get about 25% more battery life out of them, and they discharge more flatly, so they tend to hold up their voltage until they are exhausted (as opposed to gradually dropping and dropping over they lifespan. If you are bold, you can gently unsolder the coin holders on the board, and bend them a little taller, to accommodate the larger SR45 battery, which has about double the mAH life of the SR41. I did all these things and tested the lifespans. The SR45 won't hang off the edge of the board, although it is a little taller, but I did not have any trouble putting the boards in with those batteries in it.
