Software is a craft. Why would we stop practicing our craft as we get older? Do cabinetmakers stop making cabinets? Not as long as their hands can hold the tools. I'm 53 and still a working developer. Over my career I've worked with languages from 8086 assembler and Pascal to C++, C#, and now primarily Python. I am called on now to do more leadership, and my judgement is sought on architectural matters more than when I was in my 20's and 30's, but the primary skill remains my ability to comprehend a set of requirements, and from the infinity of potential implementations distill one that will satisfy those requirements in a robust and maintainable way. It's a valuable skill, and since it has been feeding my family for a couple of decades now I see no reason to let it wither.