Being able to create an alias for use on for example online competitions or surveys, where there is no need to keep a record of that alias or use it again after a certain date. This would help keep the list of aliases in the vault down to a manageable level.
In such a situation of for example entering an online competition, the user could create an alias and enter an expiry date for the alias. The user could then align the expiry date with a date after the competition is finished and winners contacted.
This feature would be useful for interactions with online sites, where the user does not expect an ongoing relationship and therefore need for an alias longterm.