I think a lot of people are confusing reservations and tickets. Little has really changed since the paper ticket days--the same logic is basically implemented in an electronic form, and hasn't changed substantially.

I've rarely had a problem with AA extending holds beyond 24 hours, but the fare is not guaranteed past that point if its extended via a time limit, however, its fairly rare that the fare is pulled. The usual problem is the TL expires and the space is cancelled, and then it gets repriced into different (usually more expensive) inventory.

There are still a couple of loop holes to that policy, but not many. Anyone who's ever used a voucher in person can probably figure out at least one of them.