It all depends i think on how many foxes there are in the area. I rattled a hole on wednesday, fresh scent but nothing in it, then had a dog and vixen out it on saturday. Ive also had the same fox bolt out an earth 3 weeks in a row out an unnetted hole, so they definately come back and re use them.
I think if the earth has been dug, allow a couple of weeks, if it hasn been dug, a week should be sufficient. Its just your luck.
FTB