As an early retiree, 39-year-old Steve Adcock and his wife Courtney, 36, have the vast majority of their $1.2 million net worth sitting in investments. But even though the couple expects to live off of this money for the rest of their lives, they rarely spend any time checking on it.

That's because they made the decision early on to never try to time the market, instead opting to keep their money in targeted retirement funds. While timing the market successfully — that is to say, buying individual stocks in the hopes that they will increase in price and then flip for a profit — can be lucrative, Steve says it is "a recipe for disaster."

"None of us can tell the future," Adcock tells CNBC Make It. "[People] suck at timing the market."

Adcock says that his status as a retiree makes him even less likely to try to pick stocks because he and Courtney have very little traditional income to fall back on if an investment were to backfire.

Instead, Adcock believes that investing "doesn't have to be hard." The funds he invests in are diversified to reduce risk and automatically shift his portfolio balance away from equities, which are more risky, and toward bonds, which are less risky, as the years go by.

In addition to helping give him peace of mind, this strategy also helps Adcock save time. He spends very little time each month reviewing his investments to make sure everything is in order.

"We don't have to really watch it all that much," Steve says. "We don't have to re-diversify because that happens automatically. So for our expenses, for the way that we manage our money, we might spend an hour a month at most looking at them and making sure everything still makes sense."

The couple still sells investments, but only when the market is up. They are careful to not withdraw more than 4% from their retirement portfolios each year, and try to only sell enough to keep their checking account flush with two years worth of expenses.

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