At a time when wireless carriers are doing away with unlimited data and moving towards shared data plans, U.S. Cellular has announced it is running a special promotion that allow customers to sign up for unlimited 4G LTE data on smartphones for $40 a month with a two-year contract from now until January 31st, 2013. Once the two years are up, customers will then be forced off the LTE all-you-can-eat plan. For an additional $20, U.S. Cellular customers can also add on unlimited 4G LTE tethering. U.S. Cellular recently added 30 new LTE markets to its growing network earlier this month to round out a total of 58 markets with high-speed mobile data. If your area supports U.S. Cellular’s 4G LTE network, the deal is a steal.