All those credit cards from college that initially hurt Chua, for example, helped him down the line. That’s because he never cut them up, creating a longer credit history and a higher average age across his accounts. Both of those numbers feed into the 15 percent or so of a FICO score based on the length of your credit history. A virtuous cycle develops when you have good credit, says Chua. More companies offer you credit, which raises your total credit limit, which means you can make bigger transactions but still use the same percentage of your total credit.

Chua used to work with Kelman, our FICO score-obsessed husband, whom he calls his “credit-card mentor.” Kelman was Credit Karma’s lead analyst in data sciences, able to crunch a huge pool of anonymous information. “I had access to the credit reports of millions of people, and you just correlate the variables,” says Kelman.

Kelman’s own credit saga is much more complicated than Chua’s, and involved a lot more gamesmanship.

His family had arrived in America from the former Soviet Union a year before he started college and got his first credit card. He was dumbfounded by the concept. He described the card as a potent symbol of capitalism, “a rectangular bundle of joy” that at the time seemed to signal a “crowning achievement.” For about 17 years, he had great credit.

It might have stayed that way had he not charged the cost of a move from New York to Silicon Valley. In 2010, he decided to default on four credit cards, plotting out a high-stakes strategy: He would stop paying his cards and then try to negotiate with issuers just before hitting 180 days of non-payment. Accounting rules require credit-card companies to write off bad debts at that point, and he figured they don’t like doing that.

Through perseverance, well-rehearsed tales of woe, and the unplugging of his land line to avoid collection calls, Kelman reached settlements averaging 30 cents for each dollar he owed. His credit score, however, fell below 600.

His rebuilding effort was assisted by his diligence in paying down student loans while keeping credit card companies at bay. It also helped that a few older cards survived (though his limits were cut dramatically), keeping his long credit history intact.

Going forward, Kelman charged very little on his cards, using less than 5 percent of his overall limit across cards and less than 30 percent on each one. He sometimes paid his balance more than once a month, disputed minor inconsistencies in reports, and asked issuers for higher limits. He rarely applied for new credit.

After two years, he had a credit limit of $40,000 and a score in the low 700s. When the seven-year-old negative information fell off his report, his numbers jumped into the low 800s. By July 12, his FICO score was just 8 points short of perfect.

While all this strategizing can pay off, the reality is that it’s a lot of effort. And what does a perfect 850 bring you? Very little that you couldn’t get with a lower score, it turns out. “There is no incremental value to having an 850 score over, say, a 760 or 780,” says Ulzheimer.