With people living longer, it is important not to view retirement as the finish line for your retirement investment program. At the same time, it can be equally important not to view post-retirement investing as business as usual. With Americans typically living about 19 years after they reach the traditional retirement age of 65, it is usually necessary to keep some growth components in your portfolio after leaving the workforce, primarily to help purchasing power keep up with inflation. However, in assessing how big a role growth should play in your investment mix, the key is to recognize that a profound shift in risk exposure occurs once you retire. The source of that shift? The transition from positive to negative cash flow.