Most of us will buy only one or two new homes in our lifetime. We don't follow the housing industry closely between purchases, and we think improvements in things like insulation and windows over our current home represent the latest technology. New home buyers often believe the insulation levels in a typical new home make it energy efficient. The simple answer is as much as you can afford.
Houses last a long time.
The more insulation you add now, the better you are protected against future energy costs. The small extra cost of getting the insulator to blow a few extra bags of insulation into the attic will pay dividends in the future. R2000 builders have been substituting rigid foam insulation and metal bracing for board or plywood sheathing to obtain walls of R-25 or more. Rigid insulation more than doubles the R-value at the studs, headers, and other framing in the wall. The only extra cost is more insulation.