I don't think it is correct to put it in terms of age.
In my small example, I am 53 years old, played a few GTx having fun but never fully committed, until now (where I am as committed as life allows me, so far from full).
As you probably know I am not lightning fast but I have certainly improved a bit over the last year.
The idea that I will get worse as I get older doesn't even occur to me. Of course it is happening, reflexes, pace, etc. etc. will only get worse, but I hope to make up for that with study, attention to detail, and use of the brain.
The end result will be the algebraic sum of these two forces going in opposite directions.
Perhaps for those of you who are already ultra-rapid part the achievable improvement is maybe marginal, or at least translates into fewer milliseconds, but for others who are just getting into it and are studying from scratch or close to it I think there is still quite a bit of room.
Of course as our friend Albert said (assuming it is him, and assuming he is worthy of credit since he is not even a user of this forum):
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