My experience has been that Sterno tends to leak or vaporize (fairly warm environment), leaving me with unopened cans that have lost their contents. These cans are the type with a friction fit lid - perhaps there are other types of packaging that work better.
My understanding is that it is basically jellied alcohol. If so, just plain alcohol will keep, and heat, much better in any of several types of burners.
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Geezer in Chief