You didn't say if you were travelling to and from the same city pair on a regular basis? If you are buy a one way to your "travel city", then from that point forward buy round trips that originate in your "travel city". This worked out great for me when I travelled back and forth to Dallas for a year, and it is not against the rules. My "one way" ticket was on Southwest so I didn't blow the budget on a "big airline's" one way ticket price. The other big benefit for doing this was that since my Monday morning flight was my return ticket if I missed it wasn't the end of the world since I was in the middle of an itinerary they had to get me back "home" I was usually able to get on the next flight which was often.

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Rachel
CO - Platinum
Hilton - Diamond
SPG - Platinum
The Princess' Pictures