Battery does not just degrade with power cycles. It also degrades with time. Not sure about the numbers for LFP, but it's something you need to take into account. For some areas time may be a more important factor than cycles. If it does a full cycle every 3 days or so, it'd take roughly 25 years to reach the cycle limit.
It's also important to remember that capacity will be reduced gradually. After 25 years both the energy storage capacity and power output of batteries will be seriously reduced, while the gravity-based system will most likely still be at full capacity.
I still think the estimate may be too high. Especially taking into account that these systems will compete in the future at a time where battery costs will be lower. But it might still make sense to build gravity based systems for a while to make sure all the lithium we mine goes to batteries for transportation.
It's also important to remember that capacity will be reduced gradually. After 25 years both the energy storage capacity and power output of batteries will be seriously reduced, while the gravity-based system will most likely still be at full capacity.
I still think the estimate may be too high. Especially taking into account that these systems will compete in the future at a time where battery costs will be lower. But it might still make sense to build gravity based systems for a while to make sure all the lithium we mine goes to batteries for transportation.