I closed my Ameritrade account prior to the six month period that it was required to remain open and Ameritrade reversed the 2,500 United miles they had previously given me. I didn't really care since I had already used the miles but I have never had such a thing happen. I tried to explain to United that I should be able to open a new mileage plus account since I have no incentive to fly United because I must first go through my negative 2,499 miles to reach zero, but they were unsympathetic. I am posting this as a warning to anyone considering closing their Ameritrade account prior to the end of the required period.