Improving on the yeast bottle
I want to share two things. One is a tested idea that I have used with great success, one is a new (to me) idea.
Cranberries contain a chemical which interferes with yeast and slows down their metabolism. This is one reason why cranberry wine is not a thing. Careful addition of cranberry juice to a yeast bottle will slow down the fermentation and make a bottle last longer (while producing less of course). I do half a tablespoon of cranberry juice (obviously, it has to be real cranberry juice) per liter of sugar mix. It doubles my run-time while providing acceptable CO2 levels from one bottle for a small tank (less than 10 gallons).
The other idea is a way of getting a long, stable run time from yeast bottles. If the sugar solution was dripped into an active culture, there would be no boom and bust like when you start the mix with 100% of the sugar available right away. In addition you could possibly stop adding the sugar at night to greatly improve runtime. However actually achieving this aside from daily manual squirts of sugar might be a challenge.