I'm 30 now, and feel like I've been running on fumes ever since. I am still interested in software architecture at a conceptual level, of course, but suffer from immense fatigue at the keystroke-based deliverables aspect. It's always a motivational struggle to write even a little code, with few exceptions. I procrastinate horrifically, because I find it tedious.
Some of it may be because my work entails dealing with fairly uninteresting and unexciting things, and some of it is the cash flow schizophrenia of constantly operating at the very margins of economic survival, but above all else, it's just psychological, cognitive and physical fatigue. I'm also fairly extroverted and have always been interested in the social and political dimension of what I'm doing, but, through eight years of self-employment, have pigeonholed myself into a solipsistic role without a collective--rewarding to those who crave peace, quiet and code, but not at all catering to my particular reward centres. I love selling what I do, but the dreaded implementation of what I just sold is like pulling teeth. Deprived of a collective, recognition, the competitive aspect, and any sense of larger purpose, it's a real challenge to get myself to work on code.
In retrospect, I probably would have been better off sticking it out in corporate America and tracking myself into technical management. However, I left the employment world at age 22 and decided to hole up in a business model where I'd be most economically rewarded if I could get myself to write more than a few lines a week.
I am deeply specialised in a niche vertical that can pay well, so one would think the money would keep me going (I can easily bill $250/hr for what I do), but it doesn't. Some of that is a business and life problem, but some of it is that I just don't care enough to pound code anymore at virtually any price--though, of course, that's not to say that taking the bricks of economic stress that come with a bootstrapped eight-year consulting-turned-product death march off wouldn't help.
I still do it, but it's taken me five years to write a slightly half-assed software suite that an energetic and motivated programmer could have done in far, far less time.