What is the ruling on not shortening prayers and performing Sunnah prayers during travel, and does a traveler returning home shorten prayers, and is it sufficient for a traveler to recite the supplication for leaving the home only upon departing his home, or should he say it every time he leaves his lodging during travel?

Shortening prayers during travel is a Sunnah (definition) that the Prophet, peace and blessings be upon him, consistently observed. Some scholars are of the opinion that it is better than praying in full, though one who does not shorten their prayers, their prayer is valid, despite their abandonment of the Sunnah. As for the regular supererogatory prayers (Sunan Rawatib) during travel, they are recommended according to the majority of scholars. A traveler continues to shorten prayers until they return to the place from which they began shortening, or if their stay discontinues the ruling of travel. The supplication upon leaving the home is recommended for both travel and residency.