While I don't know how Kia has it programmed, it would be nuts for them to make it charge to 100% and drain to 0% every cycle. It would reduce the battery lifespan by YEARS.I've also wondered about this, I think we'd need Kia assistance for an accurate answer.
My guess is that if your daily mileage is for example 20 mi, charging only to that level would provide some benefit, but I really am guessing.
The other related consideration is that battery life is also a function of the number of discharge/charge cycles, so ideally you'd want to minimize those as well.
FWIW I've read that Chevy Volt does indeed include this consideration in its programming, reserving battery capacity for later in the vehicle's life.