What time benchmark on a mental 'Skill Decay Scorecard' signals that a professional's learning curve has flattened?

Answer

If the last meaningful entry is more than eighteen months old

The suggestion is that if the last time a professional intentionally learned a major new software version, gained certification, or successfully advocated for a process change based on outside research is over eighteen months ago, their learning curve has likely flattened.

What time benchmark on a mental 'Skill Decay Scorecard' signals that a professional's learning curve has flattened?
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