Currently it is not possible to set an expiration date on any of the Talent Trials.
Candidates have 4 days to complete the Talent Trial online and are sent an email reminder 48 hours before the expiration.
They have the option to request more time from their accounts. If they request more time, you will receive a notification in-app so you may reset the Talent Trial from their candidate card.
You can also choose to reset it before they even request it. Once it has expired, in their candidate card you will see the option to reset like below.