Applying the same numbers to the next time isn't relevant when making a comparison. Applying the same differences between methods to the next time has relevance, because it's the differential that will remain even when variables of weather and meats alter the totals.
For a snake to "last longer" than the S 'n S you'd almost certainly have to be using more charcoal, less air, lower temp, less meat/easier meat, perhaps a S' n S 1.0 instead of a S 'n S 2.0 and so on.
The heat loss alone, through the bowl wall when not using a basket of any sort, is no joke. That lost heat costs extra fuel and air to overcome for a given grate temp, yeah? I honestly did not read where your anecdote accounted for any of those variables.