How long the nitro cartridges last depends on the size of the cartridge and the amount of brew you’re using it with. For instance, a 2.8-ounce cartridge can be used with 64-128 ounces of liquid, depending on the length of the pressure release. Larger cartridges can be used with higher volumes of liquid or for more batches, again, depending on how much pressure you’re using to infuse the nitro into your drinks.