I have been following this thread for a while, so I suppose it's time to throw my 2 cents in the bucket. I think, and this is total theory, the reason you can only get the mix to last around two weeks, and the reason the gelatin method works, is you must consider yeast is alive and reproducing. If there is plenty of food, there will inevitably be plenty of yeast, regardless to the initial yeast amount. If you made a 55 gallon drum diy unit, and kept the same proportionate amount of sugar, but only put in a teaspoon of yeast, it may take longer to really get going, but eventually as the yeast population grows, you are just going to produce an insane amount of co2 over maybe a 2 1/2 week period. I am guessing the gelatin restricts the movement a bit and thereby the access to the sugar.