It can be tricky, because once you give someone lawful access to the vehicle, it's not necessarily stealing if they have the vehicle. Under the laws (in most states, maybe all of them) taking a vehicle for temporary use when prior authority has been granted, or can be assumed such as in family situations, rental car agreements, or unauthorized use by chauffeurs and others having lawful access to the vehicle, must not be classified as motor vehicle thefts. Rental agreements will specify a date of return, and truck leases between driver and owner should also have a clearly defined date of return, if not a specific date, then something that creates (triggers) a specific date. Most states (if not all) have other categories such as "deception" and "deprive" where the theft can be placed in order to prosecute. Theft by deception is a common one for writing bad checks, but if you lease a truck for s specific purpose and then stop using it for that purpose, that's also deception in many instances, and will void a contract.Permission to possess a vehicle one doesn't own is construed as open ended, meaning they don't ever have to give it back? I can't believe the law allows that. But I guess it's best to cover that contingency when writing a contract, with something like "must return vehicle to specified location within 72 hours of notification from owner to do so."