i have 10++ years more, but i don't notice such.. fatigue. 2..5+ hours.. no problems (even with fingers-typing-wrong-keys/order-much-more-often). What i do notice though, and not only in coding, is.. kind-of creeping-boredom. Growing tired of certain things going the way they go, too quickly. You know, the deja-vu feeling when you see something developing certain way, and seeing it go exactly there. Thousand times..

But i haven't stopped learning things, apart of the software-making-related, 2 years ago went into e-foiling, and some half-related more-technical adventures. So maybe that is keeping the dementia at bay..