How long will bell's palsy last in a 22 year old?

Varies. It can take from a few weeks to many months for facial motion to return after bell's palsy. The more severe the initial weakness the longer it will usually take to recover but this is quite variable and not related to age. Most will eventually regain normal function.
Everyone's different. Most cases i'd say resolve by 6 months. Some resolve within a few weeks. Rarely some may have residual symptoms even after 6 months, especially if your nerves regenerate incorrectly. I feel for ya, make sure your eyes are adequately protected and see your ophthalmologist.
8->12 weeks. In uncomplicated bell's palsy, you should begin to see some recovery of function in 8->12 weeks. If there is no recovery of function by 12 weeks, re-evaluation by EMG may be necessary. If the bell's palsy is the result of lymes' disease, treatment of that disorder is imperative for the resolution of the bell's palsy.