The battery is designed to last for 50,000 km at which point ~70% capacity should be retained. Hence, the number of charging cycles can vary based on charging behaviour.
As for life of the battery pack, Ather provides a 3-year unlimited distance warranty on the battery pack with a 70% or higher battery capacity retention. With this, the battery pack should still hold enough capacity to not have an impact on the performance. After the warranty is over, the battery capacity will keep reducing in capacity gradually and should not need an immediate change as long as the usage of the vehicle is within the range of the vehicle at that point.