Hi
Welcome to the forum!
The primary treatment of all mucoceles is open surgery. If the mucoceles are not surgically removed they get infected and can cause local, orbital (related to eye) and intracranial (related to brain) complications.
After removal the general prognosis is good and continuous post operative follow up can detect a recurrence early.
However on net and without examining it is difficult to give a confirmed opinion. In general excision of the whole mucocele (not obliteration) will be beneficial. However if this is not possible surgeons go for obliteration surgery.
An ENT surgeon specialized in mucocele surgeries should be able to guide you better after examining your husband and by doing a CT scan or MRI of the sinus. Hope this helps. Take care!