That's a 'rule' I haven't heard before. Perhaps you mean diy plates made with a Liquid Light-type product (??) It is possible to overcook (digest) an emulsion in the last stage. If you do, the plates can very slowly pick up fog over time. Of course, there's no requirement that you ruin the broth I suppose it also depends on the definition of 'short' shelf life. I deliberately put aside a plate for a year and then exposed it to test. It seemed as good as new.
Originally Posted by Two23