Here is an interesting paper on SWR's for retired persons that applies Gompertz Law of Mortality
http://www.ifid.ca/pdf_workingpapers/Spending_Retirement_Vulcan_14MAR2010.pdf
The paper assumed a "standard" retirement age. I was wondering if anyone had looked into these types of calculations Early Retirement scenarios.
For an explanation of Gompertz Law of Mortality see http://gravityandlevity.wordpress.com/2009/07/08/your-body-wasnt-built-to-last-a-lesson-from-human-mortality-rates/
Note the reverse s-shape of the survival rates over time.