Is it permissible for a traveler to shorten or combine prayers if he intends to stay for more than three days without specifying a return date?

It is permissible for the traveler to shorten the four-rak'ah prayers if his journey is lawful and its distance is not less than 83 kilometers after passing the houses of his village. He is also allowed to combine the Dhuhr and Asr prayers, and the Maghrib and Isha prayers, either by advancing or delaying them. If the stay in Ta'if is less than four days, or if the time of return is unknown and it is not highly probable that the stay will be four days, then shortening and combining prayers are permissible. However, if the stay in Ta'if is a full four days, excluding the days of arrival and departure, then the traveler is considered a resident, and it is not permissible for him to shorten or combine prayers.