The wachtelhund does not work cold tracks of healthy game. I cannot give a very precise answer here, but I would guess that a track older than an hour would interest the dog very little. However, older articles describe that the wachtel (once upon a time at least) could work night tracks of fox and hare, so it may not be completely out of the question with the right dog and training. That said, I am in the process of getting a hound breed for my own fox hunting for the very same reasons - a dog that will work cold tracks and stick to the same fox for hours. This type of work is not what the wachtelhund was bred for.