There is a general withdraw convention which is assumed by most withdraw calculators which affects withdraw rates, investment strategy and taxes paid.

The convention is to withdraw from taxable accounts first, tax deferred accounts second, and tax free accounts third.

The convention has some good logic and tax advice built in.

1) Withdraw from taxable accounts first allows tax deferred and tax free accounts to compound longer, allowing each to increase in value.

2)Withdraw from tax deferred acounts second. This allows tax free accounts to compound longer.

3) Withdraw from tax free accounts last. This maximizes the compounding on withdraws you will never pay taxes on.

A slightly more flerible take on this is to attempt to maximize the tax free account value.

This requires some tax planning assumptions:

1) A person needs to assume their withdraws are relatively consistent (increased only for inflation).
2) A person needs to assume the US will maintain a tiered tax structure. Teired tax structure means there will be a poor 10% tax bracket, middle 15% tax bracket, upper middle 25% tax bracket and a rich 28%-33%-35% tax bracket.
3) A person needs to assume these brackets will have income caps close to the level of spending/withdraws desired.

Example- a person needs 100k of spending per year. This required an investment portfolio of $2.5 M.

Assume there is $750k in taxable accounts, $750k in tax free accounts, and $1 M in tax deferred accounts.

100k for a married couple is in middle of 25% tax bracket. With creative withdraw strategies (which defy traditional convention) a person can save themselves 10% on taxes.

I will assume the 750k in taxable accounts is primarily invested in dividend paying stocks yielding 3% ($22500 in income taxed at 15% is a net of $19125 in income).

I will assume the 750k in tax free accounts are growth oriented with some bonds.

I will assume the $1 M in tax deferred accounts are income oriented with some growth.

Overall portfolio is 60% stocks and 40% bonds.

The basic withdraw strategy is:

1) withdraw cap to 15% tax bracket. I will use $66100 in this example. Because of exemptions and similar tax deductions, it''s probable a person could withdraw $82k and still have only $66100 of taxable income.

2) Use the dividends for income from the taxable account. This adds $19k of income to the $66100.

3) Either sell some of the taxable account, or withdraw some from the Roth account to keep marginal tax bracket at 15%.

$100k-$66.1k-$19k=$15k needed.

The basic premise here is to keep the tax rate low over an extended period of time. The extra 15k would probably be withdrawn from the taxable accounts first to allow Roth accounts to compound longer.