Most people who are infected with laryngitis get over the laryngitis infection within 2 weeks.
If the Laryngitis lasts longer than 2 weeks then you should see your doctor about it to get treated as it might be a more serious infection of Laryngitis.
Acute laryngitis lasts on average of 2 weeks and if lasting longer then a doctor should evaluate the Laryngitis and may have to prescribe you some more powerful medicine or antibiotics to treat the Laryngitis infection.
If the person has a fever with the laryngitis then they're likely contagious so avoid being around that person or wear a breathing mask just to be safe.
Once the fever is gone the person is usually no longer contagious with the laryngitis.