In a recent report How "Transitory" Is Inflation?, Research Affliates explains why it thinks "the US Federal Reserve Bank’s expectations for the speed of reverting to 2% inflation levels remains dangerously optimistic" and actually expects it to take around 10 years. The further above 3% it gets, the longer it takes to revert.

Returning to 3% inflation, which we see as the top limit for benign sustained inflation, is simple from 4%, difficult from 6%, and very difficult if we are at 8% or higher. Reverting to 3% from above 8% typically requires 6 to 20 years, with a mean of more than 10 years.
 

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