When does a human brain fully develop to its maximum capacity?

[Xenolith]

Some say 25, some say 40, or even 50. Will there be any distinctive changes with yourself that lets you know? Does your taste in art change? Do you acquire increased eloquence? Does your cognition change drastically? How different will you be in comparison to yourself 7 - 10 years ago and what will be the significant differences? I need to know.

[MacGuffin]

Why did you start this here?

Physically the brain starts to degrade around the same time the body does - in your twenties.

[A Schnitzel]

I know your VO2 max capacity reaches it's peak at 25.
It gradually declines after that. If you keep your fitness up, you can still stay very close to your peak VO2 into your late 30's. Remember it's not the maximum capacity that is important, but the percentage you can use for an extended period of time and how long you can use it.

The same can be extended to the brain. Look how many brilliant professors there are in their 40's or later. While they may not have the thinking capacities they had in their 20's and early 30's, they make up for it in other ways. They are able to concentrate longer, are more organized, are more emotionally stable/secure, and they also have more pure knowledge and experience.

[walfin]

NEVER.
For me, develop to maximum capacity means ability to use the maximum possible amount of your brain (100% - processes necessary for life etc etc).
It'll never happen.

[Ferrus]

Much like the body, the brain can retain full capacity till age 70 or thereabouts, if it is judiciously trained and exercised.