Vaping is still a fairly new alternative to smoking, so we don't have a strong track record to predict device longevity. What we do know is that a vaporizer that's properly cared for should last for years, though if you're using a battery-powered device expect to replace the power source after 150-300 charge cycles (plan on gettin 5-6 uses out of your device per charge, so somewhere in the range of 1000 sessions). Some devices have an integrated battery which will limit their overall lifespan, while others have replaceable batteries that can be swapped out when they stop holding a charge.