Originally Posted by
BLI-Flyer
Another option is to book a round trip ticket now with a return date within the 331 days, but change it later on and pay the change fee, if any.
This may not work, because many tickets are only valid for a finite period from the date of the outbound flight.
The 331 days is often, like a Saturday-night stay or maximum stay, part of the fare rules that comprise the deal with any given fare. I guess the airline's idea would be for you to buy a one-way ticket now, then buy a one-way ticket for your return later. Hopefully you can find a fare product that can get you around that.