Roth Conversion Ladder while minimizing taxes

[Felipe Ocampo]

My wife and I plan to retire in about ten years. We will probably have $500k in taxable accounts and $500k in 401Ks. Initially we will draw about $40k each year from our taxable accounts. Since withdrawals from taxable accounts don't count as income, both the income tax rate and our capital tax rate should be 0%. Therefore, I think we should also plan to do a Roth Conversion Ladder on $19,049 (less than the $19,050 to still be in the 0% income and capital gains tax bracket) to minimize taxes paid on some of the 401K money. Otherwise, when this money is withdrawn from the 401K we would end up being in the 12% tax rate. 

The converted money would end up in a Roth IRA where it would grow tax free or could be withdrawn tax and penalty free. This is what it would look like:

$40,000 (Taxable account) $19,049 (Convert Roth IRA to Traditional IRA: this money can't be used in 5 years)

I would essentially repeat this over and over again and save tens of thousands of dollars in taxes. 

Is there a flaw in my logic here? I would really appreciate any comments or insights.