I've been a software developer for 17-18 years now. Mostly I've done web sites and web applications (some of the front-end stuff, but mostly Cold Fusion, classic ASP, .NET and more recently, MVC.) In that time, I've had 11 jobs, so you can figure out that the average length of my jobs was about 1.5 years. (Most are 2-3 and one was nearly 6, but a few were much, much shorter.) While I've had, probably 11+ different titles, almost all of the jobs were the same. I implemented the provided requirements. Personally, I think I'd do well in a people-centric management role, but the problem seems to be that I'm pretty good at implementation, but I don't stick around, grease the right palms, and end up in a position where that sort of career shift opportunity (I'm loathe to call that "progression" or "advancement") would present itself.
Now, I'm still a good 5-8 years away from FIRE, depending on a few variables and decisions going forward... and I am tired of being in this developer/implementation role. I'd enjoy being an architect, developer manager/team lead, or even fully independent (I enjoy freelance projects where I develop, sometimes teaming up with a designer). But there's no easy way for me to get there. (Well, maybe I could try to apply for that kind of job, and try to fake my way in...) So I'll likely have to grit my teeth and stay on this path for now.
For the most part, I don't regret keeping my head down and implementing software all these years, but when I was in your position, I felt like it was the place I wanted to be, so I just changed jobs to get a raise. I've yet to work anywhere that cared enough about what I wanted to give me a big raise just to keep me around. Career progression is what your manager and employer want. Promote you out of your comfort zone, and replace you with a less expensive new developer. Now it's your domain knowledge and experience in the company that's valuable, rather than your skills in software.
I have a feeling that doesn't answer any of your questions, but it might give you some insight into your future. As someone who's aware of the "high earner, low spender, early retiree" path, you might be able to plan out the next several years of your life/career much more intelligently than I have. (As said before, I've done this over 17 years, yet still have quite a few to go before I'm financially independent.) So if you can keep your working career short enough, you might be able to skate by in low-responsibility limbo just long enough to reach the finish line. On the other hand, if you're still in the work force 10 years from now, you might be kicking yourself that your options are a little more limited, and you can't rapidly accelerate your plans through advancement and promotion.