Three months before his trip, by chance, Jon learned his passport needed to be valid for at least six months when he entered France, and an additional three months beyond his planned departure back home. He immediately applied to renew his passport and got it in time. Had he not discovered his passport wouldn't pass French passport rules, his trip would have been over before it started. His lack of knowledge about passport regulations could have cost Jon several thousand dollars.
While US passports for adults are valid for ten years from their date of issue, the problem with trying to maximize one's ten year passport term is that many countries won't let you use your passport as it nears expiration.