Once the current โ40 litreโ (about 400 grams of CO2 from memory) bottle runs out, Iโll be installing the โbig bottle conversionโ kit - along with the 6kg CO2 bottle - after about 2 x โ40 litreโ CO2 bottles, Iโll be ahead.
Naturally you have to add in initial cost of the conversion kit and the โoutrightโ purchase of the first CO2 bottle - but if you go through soda at a rate of knots, itโs still not going to be more than 2 years and you are ahead. Along with not having to go back and swapping a smaller 40 litre CO2 bottle regularly.