The lifespan of AC gas or refrigerant can vary depending on several factors such as usage, maintenance, and quality of installation. On average, AC gas can last up to 10-15 years if the air conditioner is properly maintained and there are no leaks in the system. However, if you notice a decrease in cooling performance or hear a hissing sound from your AC, it may indicate a gas leak, and you should contact a professional AC service like Ruban Home Services for inspection and refilling.