Should I periodically delete everyone from the Unsubscribed list?
Hi bb1classic, welcome to the forums! The short answer is no. You can't actually delete subscribers from a list's 'Unsubscribed' list, just set them as active. You don't want to do this unless someone explicitly asks you to re-subscribe them to your newsletter. Same goes for your suppression list.
Don't forget that you can change your unsubscribe settings for individual lists, if you would prefer to not have unsubscribed email addresses removed from all your lists.