How often should I mix up a new batch of DIY CO2

I most often see every week to two weeks from folks on the board. When I was doing DIY injection I did it every week, but our house stays warm and that sort of speeds up the yeast life cycle and uses up the nutrients a bit more quickly.

I change mine weekly - I find it's easiest to maintain a steady level this way. I tried two weeks but the amount of CO2 produced really declines in the second week. Like Harlock I have a warm house, which may affect how my mix behaves. I use 2c sugar to 1/2tsp yeast - a Jello mix allows you to change bottles every two to three weeks. I tried it once, but found it much too labour intensive. In addition, there are 8 2L bottles on three tanks and I just don't have that kind of room in my fridge!

As I remember it(just barely), you have a 20 gal. with pretty good kH, correct?
You could put two bottles up on the tank and change one every 10 days for a good, continuous flow.
If you stick with one bottle, you can expect a fall-off in injection(a rise in pH will tell you) in about 10 days or so. I would suggest mixing a new batch and replacing bottles at 9 - 10 days, unless you have super yeast(champagne).
I used to use baker's yeast and all I got was 10 days for good flow. You can hold off, but it will probably cause fluctuation in pH if you do.
What are you using to seal the cap where the tubing comes out?

Len