1. Leave work, convert 401k to Traditional IRA
2. Calculate yearly expenses, convert this sum of money from Trad. IRA to ROTH IRA
3. Wait five years, repeating Step 2 each year
4. Withdraw yearly expenses from ROTH IRA as needed.
5. Repeat Steps 2-4 ad infinitum.
When you convert from Trad. IRA to ROTH IRA, you will have to pay taxes on the money you are converting UNLESS you are in the 15% tax bracket based upon all income. If you are married, that means you made less than 92k in net federally taxable income. If you are in the 15% tax bracket, you do not pay capital gains taxes. This means that as long as you are converting capital gains, rather than principle, you pay no tax whatsoever.
This money must now sit in your ROTH for five years, after which it can be withdrawn without penalty or tax as a contribution.
Thus do you access your retirement funds without paying taxes, and well before traditional retirement age.