Much of the area where I will fly my P4 is outside cell and wifi coverage so I will be caching maps on my tablet. My question (and I have a Shield K1) is what happens to those cached maps once they have been cached. How long do they stay in the cache? Do they disappear if you turn power off the tablet? One particular area I will go to I will frequent and it would be most beneficial to not have to re-cache the map every time I go over there. Thanks!