Assuming you are using a standard 20 lb nitrous oxide bottle, under ideal conditions and with proper care, it should last approximately 24-26 months. However, it is important to note that there are many factors that can affect the lifespan of your bottle including how often you use it, how well you maintain it, and the ambient temperature. If you live in a hot climate or use your nitrous oxide bottle frequently, for example, it may not last as long as someone who uses it less often or lives in a cooler climate. Ultimately, proper care and maintenance of your bottle will help prolong its life.