Q: I always find that financial planners do not make clear about upcoming expenses; they mostly talk about more and more income. For example, a statement like “you need 80 percent of your current income” — I never understood this figure. It looks like all financial advisers assume this figure. In a recent article, you advise a reader that she needs an income of $72,000. How do you come up that figure? Does it include mortgage payments? Say, $20,000? A: I can’t possibly tell you what your desired life expectancy in retirement will cost; that’s something you’ll need to figure…