Do we need to give employees travel pay if they cut their trip short?

Q: “I have employees that are required to be on long-term assignments two or three weeks at a time. To save money, I put employees up in a hotel (which is paid for) and they receive a per diem. In some cases, they are required to stay the weekend to save on travel costs. If I have a policy set up that an employee must stay in a hotel (paid for by the company) because the travel distance is too far (more than 250 miles) and the employee refuses to stay and drives home instead, am I required to pay them travel pay and mileage?” – Kristin, Pennsylvania