I used to think the 10% rule made a difference. That was before an endocrinologist told me to stay on 3 mg of until my cortisol level improved. I stayed on 3 mg of prednisone for many months without tapering until my cortisol level improved.

After my cortisol level improved, my endocinologist said I could simply stop taking prednisone. I did my final "countdown taper" of 3 mg ... 2 mg ... 1 mg ... zero over a 4 day period. I don't recommend this unless you are certain of what your cortisol level is doing. Otherwise, I would stick with the 10% reduction rule.

The other aspect of this is whether or not the PMR inflammation is controlled. I was pretty sure Actemra had that part covered. Actemra allowed me to taper quickly down to 3 mg and remain there for months. That allowed time for my adrenals to recover as my cortisol level improved.