In 2013, "Mr. and Mrs. 1500" — the pseudonym of soon-to-be early retirees Carl and Mindy — decided to get serious about their savings goals.

"I was having this horrific day at work," 42-year-old computer programmer Carl told Farnoosh Torabi on an episode of her podcast. "I was 38 at the time, and I'm like, 'There's no way I can do this until I'm 62 or 65 or whatever age people normally retire at."