You probably mean how long does the yeast last? There are a few factors. The warmer your room air temperature, the longer the yeast will produce. I had my Hagen canisters in the kitchen where it was always fairly warm. But be careful not to add water that is too warm when starting your mix - that can kill the yeast instantly. I never used water over 82-83 degrees F.
The yeast itself is probably the most important factor. Bread yeast from the grocery store only lasted about 2 weeks for me. Wine yeast, from a "homebrew" type store, produced CO2
for a month. Sometimes I changed it out after a months' time, and it was still bubbling pretty strongly when I changed it. I had great luck with Red Star Premier Cuvee yeast in a dark blue packet.