AA EXP DFW-LON, you're not doing anything wrong. Some folks here prefer - very vocally - to leave their tickets open. They fear (no doubt confirmed by experiences) that although the OWE ticket allows as many free date/time changes to your tickets as you might want, an check-in agent might be concerned that the date on the ticket you present at check-in doesn't match the flight you're attempting to board.

There have been some reports of problems, especially soon after 9/11, when travel paper was scrutinized with some paranoia. People were made to have coupons stickered or reissued, but even in those days (based on postings here) the problems were rare rather than matter of course.

I've only flown half a dozen of these trips, which makes me a novice compared to many here, and usually have a plan and stick to it. But I've strayed a number of times, and never had an eyebrow raised when I checked in with the "wrong" flight, even on AA, the hardest-nosed (understandably) after 9/11.

I personally think it's of less concern if you're flying in A or D class. The agents at the front of those lines are used to seeing tickets with few restrictions, so when you show up and announce "I'm on today's flight to xxx" they note that their computer agrees with you, and you have an A-class piece of paper for the segment in question, and it's all smiles.

So if you have a schedule and expect to keep to it, more or less, dated tickets are fine. If you expect to wander free-spirit-like, dated tickets will work, although if you're unlucky you may find an agent who needs some convincing. The rules are on your side and not the least bit ambiguous, so the convincing will eventually happen, but it may be a bother to you.

I think a downside to open tickets is that when airlines change their schedules, having a ticket with the old schedule on it will get you some accommodation from the airline, while merely having a reservation and an open ticket won't carry the same weight.