Realize the SR41, which is silver oxide, will last quite a bit longer than the LR41, and it
will maintain nearly the same voltage up until it "drops off a cliff" and goes dead, while the LR41 gradually fades.
I did some modifications to these boards in an old thread, where I changed the LEDs and changed the dropping resistor. Using LR41's
on the modified board, I got 22 hrs of battery life, and with SR41's, I got 32 hrs. I even tried SR45's ij modified batter holders,
which are physically thicker, but will fit on the board. They supposedly have 50% more mAh than an SR41, but disappointingly,
they didn't seem to hold up any longer than the SR41 before the LEDs dimmed enough to require a battery change.