As long as the site is online, administrators will have access to the back-end data.
On the front end, anyone trying to register or sponsor will be notified that those options are closed based on your registration and sponsorship end dates. Sponsorships are generally open until one month after the event date.
Most clients use their site year after year, so we leave them online for at least a year. If you want the site down, but the data available, let us know and we can accommodate that request. If you do not do another event with us, eventually, after 12-18 months, we will remove the site, and eventually, the data.