24 months is almost like a sacred number in the mobile industry. It's how long a standard carrier line contract lasts and, consequently, how long you have to pay for the device in installment chunks. It has also become the standard period for warranties and software updates and support. T-Mobile, which always prides itself as the "Un-carrier" might be working to change that game soon. Based on its website, it might start to offer installment plans that will take you three years to pay off instead of just two.