I'm a long-time reader of MMM and have plucked much of his low-hanging fruit. My savings rate is about 66%, and my earliest FIRE date is in 5-6 years when I'm 33-34, though I intend to keep earning for a few years after that to provide some extra safety and perhaps live a lusher lifestyle. While I have some expenses and opportunities that I can (and do) keep working on, I mostly feel like the goal is now to stay the course and build the stash for the next 5-6 years.
Now I'm trying to figure out what I should be thinking about next. I'm reminded of Rumsfeld's quote about unknown unknowns. I know about certain things that I should be planning for, but there's a whole set of concerns, worries, dreams, etc. that will come along as I'm building my stash, and then when I'm retired, that I am not yet aware of.
So: what big-picture advice do people have for young 'uns who have their shit relatively together? What should I be thinking about over the next 5-6 years as I build my stash? For those who are currently retired (early or otherwise), what do you wish you'd thought about when you were in my position? What sorts of FIRE life challenges could I get a head start on?
I started writing this a case study and then decided that it was more of a general question, so I've tried to avoid too many numbers/specifics. But I'm open to feedback that it's too general or belongs in the Case Study forum.