Bottle valves, nitrous solenoid valve seats, and nitrous regulators are all prone to failure. I don't know why bottle valves fail but they just do. I have never had any brand last longer than 2 years. The teflon valve seat in the nitrous solenoids take a serious beating and eventually fail after all the thermal cycling they undergo. Consider buying brands that make rebuild kits. I rebuild mine as preventative maintanence every spring, because failure is BAD and results in expensive motor failure. I don't know if you use a nitrous regulator, but they also need to be rebuilt every year. There is an o-ring in the design that fails almost every year.