Perhaps I've missed something, but is there some unwritten expectation that developers will switch careers or paths by the age of 40? I'm in my mid 40s, tried the management track, and can't see myself ever leaving the world of development. It's not like we're doing something physically arduous in this field; I love to learn and this is a job where always wanting to learn is both expected and rewarded. Why would anyone look at me askance if I'm older than they thought a dev should be?
Don't worry you'll be fine. It's the 40 year olds who don't like programming/learning who struggle, and produce the stereotypes.