Here in the UK there has been a recent big review of all of the research into all aspects of PMR in order to prepare updated NHS (NICE) guidelines for treating PMR.
The guidelines are now out for consultation and here is a link to the publication which has all of the evidence as well as the proposed new guidelines. https://academic.oup.com/rheumap/article/8/1/rkae002/7606885
I've also added it as a pdf attached to this comment in case you have problems accessing online.
It discusses failure rates with tapering and remission rates post-tapering and what's needed to overcome those by changing the guidelines. This publication is open for consultation and is for anyone to respond to.
Hope you might find it useful.
Bette