Currently, the maximum length of a suspension from practice in Tennessee is five years. The only harsher punishment is disbarment. Disbarment, however, was not permanent. A disbarred lawyer can apply for reinstatement after five years.
This may change in the near future. The Tennessee Supreme Court recently asked for public comments on a proposal to revise the rules of disciplinary enforcement. The new rules would make disbarment permanent and irrevocable and would extend the potential length of a suspension from 5 years maximum to 10 years maximum.
You can read the proposed changes here. Faughnan on Ethics questions whether these changes are necessary.