My year of trying to get easy c02 ended in a 19 litre container (water cooler bottle) that can last up to 2 weeks and i can go anywhere between 800 - 1800ppm in a tent. Small bottles made for a lot more work as they convert to alcahol fairly swifttly and then it's diminishing returns for your sugar/yeast routine. My 19 litre is a bitch to move around but it's a weekly or fortnightly change out so it's managable. Definitely go with a bigger water reservoir if you want long runs and less change overs, the big vessel/bottle always wins for me.I would love to find a recipe for diy bags, using tnb naturals and they seem to work well. Using homemade 2 ltr. Pop bottles with sugar and yeast too. Maybe a longer lasting yeast by chance?