Basically had to go to Europe for a client but wasn't sure exactly when or where from I would be returning so had to book it as two one way tickets. For the flight back from Europe it was only $100 more to book a EU-US-EU ticket than it was to fly one way. Client agreed to front the round trip ticket if I left off an equal amount of other expenses.
That was fine by me as I knew I would use the ticket back to EU and come home on miles or a cheap ticket but I ended up having to cancel that trip. If it goes back on the original card it just creates much more of a headache than it really needs to.