At age 34, we comfortably live on only 37% of our gross income. Our income still has the potential to increase but we are determine to keep our expenses pretty constant over the years (no kids) so by the time we retire our expenses should represent an even smaller percentage of gross. We don't expect to spend more (or less) in retirement than we do now, just spend differently. About 40% of our budget is already dedicated to discretionary spending and, once the mortgage is paid off, that should increase to about 60%.