Your Vuse ePod 2 should last for about 300 full charge/discharge cycles, before battery efficiency begins to deteriorate. This is common with all Lithium-ion batteries but will depend on your personal vaping behaviour.
After this period, you can still use your Vuse ePod 2 device, but you may need to charge it more frequently. Keep your Vuse ePod 2 battery charged to maintain the battery life.