I am exactly the same no joke. I try to keep mine always above 80. Not just my ipad but for my phone and laptop as well.
Right, because you never know if something unexpected will happen and you find yourself needing a nearly depleted iPad. We lose power quite often and in the last 12 months we have had to deal with a tornado and 3 different medical emergencies that meant a lot of time being spent in hospital waiting rooms.
So, yeah, we might be a little crazy but it is not totally irrational.