My Copper will be 4 in December and he has started peeing in the hall at night. It is also when I am sleeping hard and don't hear him get up. I always have pee pads out during the night and I do take him potty before we go to bed. Sometimes I take him in the night if he wakes me. I haven't come up with a solution yet, but it is nice to know I'm not alone in this problem.
