Your registry will stay open and active every 12 months after you add an item to it. So you can keep it open and active as long as you would like!
To deactivate your registry, complete the following steps:
Are you on a computer?
Go to Settings > Account Info and then check "Deactivate Account" and hit save. If you are logged in, you can find that here.
Are you using the iOS app?
Tap More > Account Info > Deactivate account.
Are you using the Android app?
Tap the three lines at the top left hand side of the app. Tap Settings > Account Info > Deactivate Account.