Currently it is not possible to set an expiration date on any of the assessments unless you are on the Enterprise plan.
Candidates have 4 days to complete the online skills assessment 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 extend the deadline of the assessment from their candidate card.
You can also choose to extend the deadline before they even request it.
If you are on the Enterprise plan, you will have the option to set the expiration date through the assessment settings. To learn more, read this article.
For more information on candidate cards, read this article here.