I rotate them so I am not using any particular battery more than the others. My DJI one is the oldest (3 years old), whereas 2 PowerExtras are almost 3 years while the 3rd PowerExtra is 2 years old. I generally get around 16 min of flight time out of all 4 batteries. As soon as Flight time stars to significantly decrease I will start replacing them. I hope to be flying my P3S for a long time yet ?.Dunno about you - but I tend to find latterly I use my after market more than the original .. you ?
Chris