You might want to take a look at IRS Publication 590, p 52, for details on distributions from your IRA. Pub 590 can be obtained from the IRS.gov website.

One way to take penalty free distributions is by signing up for what the irs calls "annuity" distributions. They are usually called 72(t)distributions in Fooldom. You take payments calculated from your life expectancy. They are designed to last for your lifetime. So typically the amount you can withdraw is abt 3% of the account balance per year. Usually your IRA custodian will do the calculation for your account, if you ask.

The rules require that you continue the distributions for a minimum of 5 yrs or until you reach age 59-1/2. Or if you are unable to take a distribution (as if asset value does not last), you can be assessed the penalty for all previous distributions. Hence, usually your investments must be conservative to conserve funds for at least the length of the distribution.