I would think that a 20 lb tank lasts about as long as a piece of string......Seriously it totally depends on the type of
stove that you have, its burner design (burners can vary pretty widely in efficiency), the number of other devices that you have aboard that use
propane, and most importantly how you use the propane fired
equipment. I knew a
single live aboard who told me he filled his tank once a year, and I had someone else talk about filling a tank once every three to four weeks. So how long is that piece of string?
Jeff