How has your wife responded to the treatment? Have the symptoms completely gone? Does she have residual difficulties? Is she on one of the Disease Modifying agents? When a person is initially diagnosed, there often is a period of time when relapses occur frequently. Then things settle down... that is if she is "Relapsing Remitting" MS. I have had this disease for 11.5 years. The first 2 or 3, I had a relapse almost every 4 months. Then I suddenly had a 3 year remission. I haven't now had another serious relapse requiring Prednisone since 2005. I do know that her symptoms were very dramatic and required intervention.
I also know that persons have been on Prednisone for many years (oral), persons with Asthma, Ruematoid Arthritis, Lupus, and a host of other conditions are given this drug when their illness becomes unmanageable or in the case of Asthma, life threatening.
If you are very worried about the useage, I suggest that you speak to a pharmacist or two, google the drug, speak with other health care providers. Arm yourself with information... correct information.