A candle having two wick columns, with each one being made up of multiple sections of ~1hr burn time, with ~30 minutes of empty space between wick sections. The two columns would be far enough apart that a flame on one couldn't light the other, but not so far that the wax around it can't melt. This may require some care with wax selection for melting point. You light one, and it melts the candle far enough to expose the other column before extinguishing, and you switch back and forth.
-- MechE, Jun 18 2014

random, halfbakery