Like every battery type, Lithium Battery life is based on the number of Charge and Discharge Cycles. A cycle means you’ve brought the battery to full charge, fully discharged it, and then fully charged it again.
Go Power! Lithium Batteries are rated for up to 5,000 cycles at 80% depth-of-discharge. Assuming you’re cycling your battery once a day, and no other factors come into play, your battery should last over 10 years.
There are several factors that would decrease the battery life, including: depth of discharge, operating temperature, and aging of materials.