Update on Walmart Propane/Butane cylinders:  I finally dug one of them out of storage from last winter and took it on a two week trip down the Basswood River and into Thursday Bay on Crooked Lake.  I also had along an Optimus and an MSR cylinders.  After a rest for several months the Walmart cyl did work properly but not always reliably.  Sometimes it would not produce a vigorous flame, kind of fading out to a slow burn even when turned full throttle, and still with plenty of fuel left in the cyl.   :o :o