New Zerolemon Battery case for M8 topic

I just saw this battery case on amazon and it's from Zerolemon. Would like to hear from anyone that has tried it. There are no reviews for it yet.
http://www.amazon.com/dp/B00PURC8M6

Zerolemon + New ROM: battery recalibration? topic

Thought just occured to me as im approaching my last full discharge cycle on my new zerolemon battery. If I flash a new ROM will I need to recalibrate the battery? If so, is there an easier way of going about it like saving a system file and copying it over to the new ROM?