Hi there, I had polymialgia for nearly 2 years, it started August 2021 and by June 2023 I was polymialgia free.I too started with 15 mgs of Prednisalone and I found by the time I got down to 6-7 mgs the key was to go dead slow with tapering. I was doing it by 0.5 mgs every 4 to 6 weeks and that way I was able to keep going until I got down to the last 0.5 mg. It worked for me but I know everyone is different.
I wish you lots of luck on your journey, and hope you will soon be doing as well as I did.
Kind regards Pat.