There are certainly challenges to the 10% recommendation once you get below 10 mg. If it were a semi strict rule then the taper would look like this:

10 mg to 9 mg (9 mg) for 1 month
9 mg to 8.1 mg (8 mg) for 1 month
8 mg to 7.2 mg (7 mg) for 1 month
7 mg to 6.3 mg (6.5 mg) for 1 month
6.5 mg to 5.9 mg (6 mg) for 1 month
6.0 mg to 5.4 mg (5.5 mg) for 1 month
5.5 mg to 5 mg (5 mg) for 1 month
5 mg to 4.5 mg (4.5 mg) for 1 month
4.5 mg to 4.1 mg' (4 mg) for 1 month
4 mg to 3.6 mg (3.5 mg) for 1 month
3.5 mg to 3.15 mg (3 mg) for 1 month
3 mg to 2.7 mg (2.5 mg) for 1 month

The above tapering plan would take 1 year. After a year, the taper is by .25 mg increments and takes another year. It would be interesting to see how many people flare before the end of the first year. My rheumatologist wouldn't have cared if I took 3 mg or less for the rest of my life.
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In contrast to the above taper, while I was on Actemra, my taper was the following:
10 mg to 9 mg for 1 month
9 mg to 8 mg for 1 month
8 mg to 7 mg for 1 month
7 mg to 6 mg for 1 week
6 mg to 5 mg for 1 week
5 mg to 4 mg for 1 week
4 mg to 3 mg for 1 week

At this stage my cortisol level was too low. I was instructed to stay on 3 mg until my cortisol level improved. It took 6 months for my cortisol level to be called "adequate." I was reluctant to discontinue Prednisone but an endocrinologist said going from 3 mg to zero was okay. This was contingent on my cortisol level being adequate and I wasn't symptomatic. I was told that I could restart 3 mg of Prednisone "for any reason if I felt the need. " I needed to keep my endocrinologist informed if I felt the need to restart Prednisone.

The taper while on Actemra took approximately 1 year. I have stayed off Prednisone but now I take Actemra instead. I would say Actemra resulted in a significant improvement in my overall health and well being. My out of pocket financial cost is currently nothing because I get a monthly infusion.

I have been off Prednisone for more than 3 years. Now I have to figure out how to get off Actemra. My rheumatologist has no plan for stopping Actemra other than deceasing my infusion dose. At least I don't worry about what dose of Actemra I need to have. That is for my rheumatologist to decide based on my symptoms and my side effects.