I'm planning on doing the five year 401k-Roth rollover technique.
Any money you roll over into the Roth has to sit there for five years before it can be withdrawn, so the basic plan looks like this:
1. Quit working, and so put yourself in a lower tax bracket.
2. Every year, roll over the amount of income you think you will need in five years. You will have to pay taxes on this rollover amount, but with personal exemptions and your new lower bracket, this amounts to paying a very low tax rate on money that you have invested tax-free in your 401k.
3. After five years, you have built this little pipeline of annual rollovers and can withdraw the amount you have rolled over 5 years ago without penalty and tax free.
Together, these steps allow you to get money out of your 401k without paying any significant taxes, ever.
The downside is that you need living expenses for five years to make this work. Part of that can come from your Roth IRA principle contributions, but unless your living expenses are very low and you have been contributing to the Roth for a very long time, they are unlikely to wholly support you for five years.
The other alternative, if you have more 401k money, is Rule 72(t) distributions. These are annual penalty-free withdrawals from your 401k before age 59.5, but they are calculated based on your life expectancy at the time of withdrawal. There are three different accounting methods, but even the most front-loaded is unlikely to provide full living expenses unless you are already very near retirement age. For someone retiring in their 30s or early 40s, it is not enough unless you have a HUGE stash.
So in my case, I am keeping some money in taxable accounts to help bridge the five year gap between quitting work and making tax free and penalty free 401k withdrawals through my Roth IRA.
Remember that there are certain asset classes that are not taxable, such as municipal bonds, and if you're going to own them somewhere in your portfolio it only makes sense to hold them in your taxable accounts.