After deactivating a Twitter account, you have a 30-day grace period to change your mind and reactivate it again. After 30 days, your account is permanently deleted. Your followers, lists, tweets and profile information are no longer saved and your username is available to anyone who wants to use it.
Deactivating a Twitter Account
If you log into your Twitter account, click the "Gear" icon and select "Settings," you will see a "Deactivate My Account" link at the bottom of the page. After you click this link and confirm your decision, you have 30 days before your account is completely terminated. Logging into your account at any time during this waiting period will reactivate your account. All of your tweets, lists and messages will be intact.
After 30 Days
If you wait longer than 30 days before coming back to Twitter after deactivating your account, your account will be gone. After 30 days, your username is up for grabs to anyone who wants it. Your email address and password are no longer associated with a Twitter account. You may be able to reclaim your username -- provided no one else has taken it -- but your tweets, messages and everything else is gone for good.