Adding a drops_today field means adding a drops_limit field. That could be something silly like MAX_INT, I suppose. Or maybe the default value of 0 wouldn't mess with scripts that use it.
Quite wrong. The element has no bearing on the chance of success. All that matters is how many total jellies have been successfully sucked today.However, I was under the impression from the Wiki that each element was somewhat independent as far as drop chance goes, which would reduce or eliminate that opportunity cost. Has that assertion been found to be inaccurate?