I was the most productive in music and painting during my 20s but I lived with the constant angst that I was running out of time and needed to get results as soon as possible. This was totally counterproductive. I understand now to produce better art you need to be totally focused in the process, and not the end result, or even worse, the consequences of the end result (fame, criticism, etc).
A pragmatic compromise to acknowledge it and manage your limited time in a psychologically healthy way.
Mathematics is a young people game, though. Very rare to push out significant results after forty.
I always see my creativity taper off when I stop paying close attention and I stop practicing the fundamentals. I think #1 gets harder because our downtime for reflection is often saturated by the busyness and distractions of life, and #2 gets harder because of physical aging in general.
Either way, the brain is creative in the same way the heart is for circulating blood. Continue shoveling in raw materials to the furnace of the mind and it will continue to faithfully churn out novel concepts.
I haven't dug in, just noticed it's age at the time of award, not time of achievement.
Eg Einstein early 20s for most of his stuff, early 30s for GR. Awarded in his 40s.
We are trying to understand the cognitive nuances from the distribution of people that can be creative.
You are reacting to a correlation, likely driven by changing obligations.
e.g. pop music, maths, poetry, physics, etc; you're done by 30. Writers/composers maybe another 10 years or so.
I say that not to be negative, but to urge any young readers who feel they have a talent to not be complacent and assume they will be an exception, or that its related to family/financial/work commitments when you see the decline in your heroes and you will just avoid all that.
Use it before you lose it!