I agree with your sleeping bag requirement.
Why a plumber’s candle? They last a certain amount of hours, between 6 and 8.
http://www.wilderness-survival.net/forums/archive/index.php/t-10433.html
The common camping lantern by UCO uses a 9 hour candle that is in all the camping stores everywhere, I have switched to their version that uses the cheaper ‘tea candle’, since I am a flashlight guy with hi-tech flashlights that run for 100 hours on single batteries, etc, and carry plenty of sleeping and wearing gear, I only carry the candles for melting snow into water, or thawing my food.
http://www.rei.com/product/838881/uco-original-candle-lantern-value-pack