After after 70 1/2 failure to withdraw the required minimum amount annually from your retirement account may result in substantial tax penalties. This rule generally holds true for 401(k)s and other qualified retirement plans.
A lump-sum distribution or removing your retirement plan assets in one lump-sum, may qualify you for 10-year forward income averaging which means that the tax on your lump-sum may be calculated assuming the account balance is paid out in equal amounts over 10 years and taxed at the single taxpayer's rate.
Also remember that the IRS will give you a break if your lump-sum qualifies for 10-year forward averaging and is less than $70,000.