I love both programming and engineering (for those who see a stark contrast between the two); but at some point, the unadorned "senior software engineer" role starts to feel rather menial (and if you will, perennially "junior") -- in the sense of always being asked to do work scoped out by others (and implicitly, not being thought of as capable of thinking about the bigger picture, technically or business-wise). Age definitely has something to do with it, also: the role that seems "hot" when you're in your 20s, what you get looked at as "mature" or "experienced" for in your 30s... but then at a certain point, there's a certain "you're still doing this?" tinge that sets in (as in: why haven't you cashed out, or started your own company, etc).

So while I'll (hopefully) always be coding for at least some portion of the day, for nearly as long as I breathe -- at a certain point I realized there was both a creative and professional -- not to mention financial -- imperative to hybridize. (Which can mean different things for different people -- but basically boils down to adopting some kind of a secondary discipline, either in terms of domain knowledge; or, yes, managing people; or delving directly into the business side of things).