micky wrote:
Once in a while in cowboy movie, someone wakes up in the morning and
turns up the kerosene lantern, without lighting it.

Is it actually possible to keep a small flame burning all night, small
enough that it doesn't waste substantial money by burning all night, at
cowboy-era prices?

Hi,
Even smallest flame gives out some heat. In dead winter that can make
quite a difference. Read the story about Napoleon's men dying from
freezing sleeping in tent but ones who had a candle burning did not die.