"if you have the fuel" is the fundamental problem. Keeping the boil going for longer will increase fuel consumption considerably.
BTW, I was off in the boiling time recommended by my questionable source. They advocate ten minutes of boiling plus a minute for every 1000 foot increase in altitude. That's twenty minutes if you are at 10,000 feet!!!
Seems like slow cooling is a really good idea.
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Geezer in Chief