How likely is bell's palsy to recur?

Depends. A recurrence is more likley if you become pregnant, develop diabetes, or are under significant emotional stress. Complete remission is likely if your symptoms resolved within 2 weeks of onset or if the episode occurred in children under 10 years old.
That is rare. It is uncommon for true bell's palsy to recur. If someone has recurrent facial weakness or paralysis, then they should be carefully evaluated by a facial specialist. And ENT specialist or a neurologist to be certain there isn't another problem such as a tumor growth or other neurological problem.