I'm an aging (late 30s) writer with a fair amount of mathematical exposure, so let me give my perspective. There's a tendency for exceptions to drive the narra

I'm an aging (late 30s) writer with a fair amount of mathematical exposure, so let me give my perspective. There's a tendency for exceptions to drive the narrative, which leads to a sense of mathematicians peaking earlier than they actually do. Mathematicans do indeed peak "young", relative to other fields, but most often in their early to mid 40s. Of course, at that point they're ineligible for the Fields Medal, but that doesn't mean they're no longer productive. Writers peak around 55, but the drop-off can be steep, not because they lose the ability to write, but because revision and publishing can themselves be brutal processes. Revision is brutal because of perfectionism combined with the inability to hold a whole book's worth of context in your head. You can't look at the whole thing in one sitting, as with a painting. You have to edit at specific levels (themes and story arcs; then subplots and characters; then scene structure and transitions; then paragraphing and flow; then line edits; then copy edits; then grammar) but they sometimes compete for your attention. Writing work that's good enough to publish and sell is easy; writing work of literary quality is much harder. Publishing... well that changes every generation. These days, self-publishing is the right play for 99% of authors, but that brings its own challenges. With age, the thing that gets hard the quickest is long-form context switching. Very few people can (or want to, or should) dedicate their lives wholesale to one pursuit. Once you start to get recognition and are invited to the parties, it gets harder to focus on writing. You spend a lot of time around non-serious players, and you become one. Lots of people turn stupid once they get popular and spend too much time with the fun people to have real thoughts anymore, and that's certainly not limited to the old. The difference is that the young can retool themselves more quickly. A 27-year-old can bounce back; he can be on cocaine-fueled benders in January, courting the nonserious players necessary to get the "tastemakers" to support one's career, and be back in his writing room by March or April. When you're older, this gets a lot harder. Older people are great when they establish momentum (leading me to question the "old people are less creative" hypothesis) but do not bounce back as well from periods of distraction or excessive comfort.