The first two days I played games, the the battery went down to 20% quick but I thought was reasonable and recharged it. ............I read that the battery needs conditioning by letting it discharged to less than 20%, is that what happened here? thanks
Modern lithium-ion batteries do not need to be 'conditioned' nor do they have 'memory issues' that plagued previous battery technologies (all of my cordless power tools have only Li-Ion batteries now). Apple does suggest a complete discharge/recharge (i.e. complete cycle) about once a month which calibrates battery monitoring properly. Depending on the device (i.e. iPad vs. Macbook), Li-Ion batteries taken through 500-1000 of these cycles will maintain about 80% of their capacity (measured in mAh).
Now, as to your experience w/ rapid and then slower loss of battery power, I have no answer; might have related to the games being played or to other features that were activated, e.g. Wi-Fi/Bluetooth radios on, screen brightness, push notifications, et al? If interested, you might want to obtain a 'battery app' (check the App Store) - I have two on my iPad. At the moment, my iPad Air 2 is 92% charged and the app shows that I can listen to 27 hrs of music, but do just 5 hrs of 3D games. Dave