This option remains available for as long as your account, and the respective game world exists. After 5 days your account will be set as inactive and you can still choose to restore your account, or to permanently delete it (this cannot be reverted, all the data will be lost).
Your account in other worlds and also forum account will not be deleted. There, you can delete your account in that world. How can I delete my account and all the data that concerns me? Deleting an account on a specific worldIf you want to delete your game account on a specific world please go to Settings → Account → Delete account.