William Sommerwerck wrote:


He didn't say where he got the 12th-power rule. Anybody know?

I don't know where it came from, or if it is accurate.
(I don't doubt or dispute it - I just don't know.)
But in 1978 I wired the 2 bulbs in the each of the EXIT
lights in the church in series. They were burning out in
3-4 months before that. Since I wired them in series, we
haven't had to replace a single bulb. The bulbs are lit
24x7, so they don't go through any on/off stress.