Originally Posted by
Xandrios
...when they start missing with upgrades or waitlists that will be visible on your booking and that means that in practice you won't be able to make changes no more.
They don't go "missing" when you're wait-listed, only when an upgrade gets confirmed.
While wait-listed you actually
can't (!) make changes online, but you can ask an agent to remove the upgrade request and then you can change your dates.
(that being said, I'd personally still wait until I knew I'd travel for sure before applying for an upgrade as a wait-listed voucher can, in theory, go through at any given time!)