I have 2 batteries here for A1466 MB Airs, 109 cycles and 349 cycles and both are original apple made batteries and both are finished, and one from a MB Pro 2015 on just 55 cycles. They no longer want to hold a charge and once the power is disconnected the units immediately shut down. I always look at batteries like lungs, they need to breathe, meaning always charging to 90-100% and running low to 5% at least once every 1-2 weeks.... this way the cells don't get to stick together for longer periods which kills the batteries performance, also charging non stop and or charging for just a few % on a regular basis can also hurt their performance. I never had any problems in doing this way and have gotten well over 1000 cycles on 2-3 batteries. Bi-Monthly re-calibration also definitely helps to keep batteries fit and healthy. Hope that helps!