Let's start with the facts: Most Americans likely will have a hard time retiring on time, let alone early.

For starters, the average retirement account balance for U.S. households ages 50 to 64 is $150,000 — and the median is only $12,000 — according to a report from The New School. Nearly a third of families have no savings at all, the study found.

Even if your nest egg is substantially larger, you'll have to account for living longer. If it's tricky to save for 30 years of income, stashing enough for 40 might seem especially difficult, said Christine Benz, director of personal finance at Morningstar. But that is not to say it can't be done, she said.