In a few weeks it will be time to book the first flight for a trip to the US West Coast where I am planning to use a Premium Economy upgrade voucher (from the MBNA credit card). The whole trip will last about 6 weeks, so I won't be able to book the return flight for a month and a half. I am wondering how this works. If I wait until I am able to book the return, I may not get the seats I want for the outgoing flight. What to do?