I think the premise you're outlining is flawed. The act of quitting and moving your 401k to an IRA does not alter the timeframe of when you will need or use the funds. Even if you are going to spend some money earlier due to early retirement, you would still be living off your investments for the rest of your life.
You might decide to take less risk with the portion of your funds you expect to use within the next 5 years, but for everything else, I think a normal investment asset allocation makes sense.
I think a lot of people assume a much shorter investment time horizon than they should. For example, we have been saving for my kids college in 529 plans, and their grandparents also started a 529 for each of them. A year or so back (kids were 11 and 13), my mom asked me if she should go with less risky investment choices. I told her absolutely not--the oldest has 4+ years until he *starts* college, but will need the money over (hopefully only) 4 years--so the overall time horizon is 6+ years for him, and 9+ for the younger since he is 3 grades behind.
Retirement in my opinion should be viewed the same way. *Starting* retirement is just the beginning of using those investment funds. Your average time horizon would be more like the midpoint between now and your life expectancy age. Retiring early if anything extends your time horizon compared to someone retiring at 65 or 70--they have many less years ahead of them compared to someone retiring in their 30s or 40s.
Personally, we have our retirement money mixed between the total US stock market, international stocks, and REIT funds. Lately all of our 401k contributions have been going into international, to raise the asset allocation vs. US funds. We currently have no bonds at all--probably should have some, but I admit to being guilty of some market timing, and I think it's an awful time to invest in bonds.
Full disclosure, we also have way too much of our net worth in a single stock that we could not sell until just recently (IPO lockout). We had no control over that until now, and the plan is to convert that into the other categories of funds over the next year or so. That stock is in a taxable account, so in our case, we will most likely have much more outside of our 401k/IRAs than in, and will be maxing our 401k contributions until retirement to get as much tax deferral as we can.