Thanks for the response. I'm interested in anyone's opinion to this question.

Two of the links seem to support the idea that adrenal insufficiency at least contributes to our need for long term prednisone. The second link says the following:

"Most of the glucocorticoid-insufficient patients could discontinue prednisolone with appropriate treatment for adrenal insufficiency."

I wonder what "appropriate treatment for adrenal insufficiency" they are referring to. The only treatment I know about is supplemental doses of corticosteroids like prednisone. Taking more prednisone won't let anyone discontinue corticosteroids any sooner. In some cases, supplemental corticosteroids are needed for the rest of their lives if their adrenals don't start producing cortisol in adequate amounts.

The third link says:
"Assessing the adrenal function in patients with PMR will contribute to establishing a more appropriate glucocorticoid reduction strategy."

My endocrinologist would not assess my adrenal function until I could stay on 3 mg for an extended period of time. Most people seem to experience flares at 7 mg of prednisone. I have read that 7 mg of prednisone is the physiological amount of cortisol that a person needs on a daily basis.

"In normal adults, the adrenal glands produce approximately 5 to 10 mg/m2/day (body surface area per day) of cortisol, which is equivalent to 5 to 7 mg of oral prednisone or 20 to 30 mg of hydrocortisone."