The last episode thoughhe runs across half the north, they send a raven Across half the realm, she then flies up all over the course of an evening
I'm still enjoying it but that was just stupid.
He didn't run across half the north, the undead army was (as seen in the vision in the flames by the hound previously) by East Watch, they went to East Watch and then walked around and found them... he just ran a relatively short distance, directly back to East Watch.
Likewise Jon Snow got back there pretty quickly on his Uncle's horse.