If the ticket could not remain open for future use, this language would have some clarification dictating that reissues have to be made prior to original departure time. I have never seen an AA ticket with USA point of sale that could not remain open without a active reservation attached.

CHANGE IS PERMITTED WITHIN TICKET VALIDITY OF
ORIGINAL TICKET.

Here is an example from Aeromexico, a carrier that, unlike AA, often includes a requirement to rebook immediately if a reservation is not to be used.

IF TICKETED FLIGHT RESERVATION IS NOT CHANGED 3
HOURS PRIOR TO TICKETED DEPARTURE TIME/ REBOOKING
IS NOT PERMITTED AND THE TICKET HAS NO VALUE.