Yes ... I felt extreme fatigue/weakness for a long time on lower doses of prednisone. I had a low cortisol level caused by adrenal suppression from long term prednisone use.

Extreme weakness/fatigue is most likely a side effect of long term prednisone use. Prednisone suppresses the ability of the adrenal glands to produce cortisol. The symptoms of adrenal insufficiency usually begins when your prednisone dose is less than 5-7 mg of prednisone. The symptoms get worse before they improve as you slowly decrease your dose even further. Never stop prednisone abruptly because that could cause an adrenal crisis.

Unfortunately the only way to get your adrenals to start producing cortisol again is to stay on a low dose of prednisone. It can take a long time for the adrenals to start functioning again. People have a tendency to increase their prednisone dose to relieve the symptoms of adrenal insufficiency before they give their adrenals a chance to recover.

The symptoms of adrenal insufficiency should be "temporary" and usually improve after you get off prednisone. At least that was my experience.