"My limited reading has told me that it can take at least 6 months for the adrenal glands to get up to speed after being suppressed by prednisone. I was sure hoping that this condition would just “poof” go away after stopping prednisone."
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There were many conditions that didn't go poof after stopping prednisone. The common belief is prednisone side effects resolve after stopping prednisone. Things seem to "gradually improve" over time but most of the side effects I experienced didn't disappear in a few days --- maybe many months or a couple of years but not a few days. My endocrinologist said some of the hormone imbalances caused by long term prednisone use may never improve.
https://my.clevelandclinic.org/health/diseases/22673-hormonal-imbalance
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The other problem is the mechanism that causes PMR inflammation in the first place might be triggered again. The risk of another flare of PMR needs some kind of medication as a preventative. I don't think PMR ever burns itself out completely. The immune system develops a "memory" for what it attacks which is detrimental when we have an autoimmune condition. If PMR isn't "flaring up" it is likely to be "smoldering" for a long time.