When using a single earphone (only one of the earphones connected and in use), this will over time result in a battery capacity difference as one earphone will have a higher power consumption than the other.
However, if always using both earphones, you may still experience a difference in battery capacity between the left and right earphone of up to 10% within the warranty period.
Rechargeable batteries are consumable components that become less effective over time, and the number of charges batteries can hold diminishes.
