iPad Air 2 battery life

I just bought an iPad Air 2 renewed. My battery life has not been great on iPadOS 13.3. I only charge this thing three times. Will this go away all the time? Or am I doing something wrong? I do not have a lot of apps installed and need this device for school. I believe the battery was replaced if it was renewed. I get about six hours of battery life and on bad days 3 to 4 hours of battery life. I was told to lead a discharge to 10% and charger to 100% and that it will go away within a week or two. Is this correct? Is there anything else I can do to extend my battery life? My device is only about four days old and I’ve only charged it three times. I also updated street from iOS 8.2 to iPadOS 3.3.