Yes, you can keep your challenge open after the deadline, or re-open it once you have processed the submissions. You can also have a separate, post-challenge phase to distinguish the challenge and post-challenge submissions. Budget will be required for both compute and storage, and will be invoiced at least once a year. Both pre-paid and post-paid invoicing are possible, please contact our support team by emailing support@grand-challenge.org to set this up.