I agree with Evo.
It strikes me that there's actually nothing particularly unusual about flying in this respect.
Any skill which has both physical and cerebral elements seems to have similar characteristics. The example that springs to my mind is playing a musical instrument where training time, total (practice and performing) time, and currency all have similar effects to those described in the earlier posts. For many musicians I would think it's fair to suggest that training time + total time is an indicator of how well you could possibly play, whereas currency (recent practice) indicates how well you will actually play today. I suspect the same argument could be used in many other fields, eg. golf, acting, skiing etc.