This has been my plan for many years. It was not very well defined, but I talked about it as, "Save as much as we can today, so we can save less in the future and have more freedom of choice." Of course, that was before I found MMM so my version of "save as much as you can" was pretty pathetic (maybe 20% of take-home). At that time, my plan was to pay off the house and get the kids through college at the same time, so our expenses would drop significantly and we could then stop saving and work in jobs that we wanted to until retirement age.
After finding MMM, and also starting to feel burned out in my current career, I realized we can't really know what will make our future selves happy. And with that new perspective, my goal is to get to FI as soon as possible without sacrificing too much of the time I have left with my kids at home (they are 8, 9, and 12). We currently have enough saved in retirement accounts such that, if left alone, we could find jobs that earn only enough to pay current living expenses and still retire at relatively normal ages (say 60 and 63).
I'm not sure anymore that I want to work that long, even in a part-time job I love, so we want to keep saving. On the other hand, I may want to work until the day I die in a part-time job I love--the point is: I don't know. And money in the bank allows me to flex as my desires change.
So my advice to you is: this sounds like a great plan, but make sure you build in flexibility to change your mind down the road. So perhaps save a little more than 200K so you could retire fully a little earlier if you decide you want to.