Sorry if this has already been asked before, but what happens if you book a flight using wallet funds before expiry and then need to change or cancel it after expiry?

e.g. have $1000 in wallet (net of change fees) from previously cancelling standard fare expiring July 31.. book comfort/latitude ticket for october, but need to change it or cancel in September. Does the money go back to the wallet with an additional 1 year expiry? Are you only allowed to make a change directly at that moment vs funds going back to the wallet? Or do you just lose the flexibility of the new ticket?