Only should see a doctor is the hallucinations are bothering them, or becoming harmful towards themselves, or other people.

Luckily, it seems as though the person you are talking about may have mild Schizophrenia if he or she hasn't had a break-down after all these years. Since it seems like it it starting to interfere with his or her functioning and/or quality of life, it is important to encourage that person to seek help. Most of the time, the symptoms can be effectively controlled with medication and psychotherapy.

It is also important to know that there is absolutely no shame in having Schizophrenia, and especially not in seeking help for it. It is a medical condition. The sooner the person gets help, the better the outcome will be.

All the best.