i went through this with mikko. very frustrating and scary as once he waited so long to pee that he actually peed for about an entire minute straight. it got better as he got older, especially now since he'll mark. what we did to help fix this problem was to give him a command, we use "go to the bathroom." so when we let him out in the yard to go, we say the phrase and reward when he does it. now when we go on roadtrips or i need him to go to the bathroom before an agility run, i use the command and he'll go.