How much do you need for retirement? The ONLY correct answer is "as much as you can get". Spending down 4-5%? If you talked to a financial planner in 1998 or 1999 they would have told you 7-8%. You CANNOT predict the future. Any assumptions used (taxes, inflation, interest rates, etc) will all be wrong. I can guarantee you that. There is NO financial plan that has EVER worked out in real life. They look great on paper but money is not math and math is not money.

Instead of focusing on things you can't control (taxes, inflation, rates of return, technological change, planned obsolescence, creditors, lawsuits, the government changing the rules of your retirement plan) why don't you focus on what you CAN control: internal efficiency. If you are as effective and efficient as possible with your money, have no over payments of taxes, no product overlap, no unnecessary costs or fees, and have maximum protection so that you never go backwards at any point in time...isn't that really all you can do?

By looking at everything from a macro-economic perspective you can have more money that any arbitrary goal or need. Then you can cover that need and have extra left over.

There is a huge difference between INvesting and DISinvesting.