Lol, I did a google, and the first hit says that a Dennerle co2 bubble weighs an average of 0.125mg
DENNERLE CO2 Bubble Counter Exact
using the 0.125mg as a base, our 2kg FE at 2bps would last 277 days. Which is 35 days less.
Today, I connected a new 2kg FE, and set my bps to 2.5bps. This should last 222 days, so I should need to replace it on 3rd May 2021... lets see how that works out!