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A lot of factors come into play.
How well was it taken care of?
How was it charged?
Rechargeable batteries do have a life span. A lithium rechargeable battery, such as in the Fitbits have a average life span of 2-3 years from when it was manufactured. In addition, during that time it can be recharged hundreds of times. But with each discharge/recharge cycle it losses a small (very small) fraction of its charging capacity.
See this thread for charging best practices. If you are not charging it correctly you could be damaging the battery
Best Charging Practices
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@umarriaz it's great to see you in our Fitbit Community! I'm sorry for the late response. However, in addition to the information that shared @WendyB, I'd like to share this help article, which provides tips about how to improve the battery life of your Fitbit Versa.
Let @WendyB and me know if you have more questions! 
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