1. Forget The 80 Percent Rule

Many retirees abide by the rule of thumb that they will need to live on 80 percent of their pre-retirement income. Scrap that, suggests Kobak.

You will be likely ticking items off your "bucket list" within the first few years of retirement. Tour Peru's Machu Picchu? Volunteer? Take gourmet cooking classes?

"Most retirees need an income of at least what they were earning just prior to retirement, to maintain their lifestyle and do leisure activities as well," says Kobak.

The flip side is that leisure spending for late-stage retirement will be correspondingly less. At 90 or 95, you will not be zipping around the globe quite as much, and likely spending more on healthcare costs instead.