If you have a mail message from TalkTalk about deletion of your TalkTalk managed mailbox then deletion is after 180 days. After 60 days the mailbox has webmail only access.
However, TalkTalk has suspended the deletion of mailboxes during this period of Government special measures so that mail users can stay in touch with friends and family. The mailbox may still be restricted to webmail only access.
It's entirely your choice. If you wish to migrate to using another mail service that's ok. You'll need to use another email address though as you'll not be able to migrate use of the tiscali mail address. If you need more time to migrate your mail use just let me know.
I'd suggest whatever you do that you save and backup your wanted emails as soon as possible. If the mailbox contents are deleted by the system they'll not be recoverable.