One of the enduring but painful truths of a CIO's career is that it's a revolving-door job by nature. With an average CIO tenure of 5 years, it's actually amazing that so many enterprise IT initiatives get done at all.I often wonder how corporate America would cope if the rest of the C-suite turned over at such a feverish rate. When is continuous disruption ever good for business?A CIO with a long tenure at one company is unfortunately an outlier, an exception to the normal experience. Yet some CIOs sail past that 5-year milestone and continue to thrive. What are they doing differently? We explored that question in this month's cover story ("Why Do Some CIOs Have Staying Power?"). We discovered a set of factors that are key to longevity: well-honed skills at executive relationship-building, the smarts to sidestep classic mistakes (failed projects, blown budgets, etc.), plus a bit of serendipity."There are always a lot of headwinds for CIOs to try to get through," says CIO Peter Weis, a 9-year veteran at Matson, a transportation and logistics firm. CIOs can do outstanding work yet still catch the blame when business models sour, strategy shifts or top management changes.Indeed, the wildest card in the CIO longevity deck is that relationship with the chief executive. Ultimately, it trumps all other factors. Consider this: More than 75 percent of CEOs are promoted from within their own organizations, according to a 2011 study by Booz and Co. That casts your C-level colleagues in a whole new light, doesn't it? Any one of them could become your next boss.Another outlier in our story is Rick Roy of CUNA Mutual, an 8-plus year veteran who navigated a CEO change, ran operations for a few years, and then returned to the CIO job. As he was getting to know the new CEO, he orchestrated his travel so he could attend some industry events with the new chief. "You have to step out of your comfort zone to engage that leader wherever he or she happens to be," he advises.Some of the best advice in our companion story ("Tips for the Politically Astute CIO") underscores the importance of humility, credibility and a willingness to share credit. "You're better off making business partners look good than coming off as the smartest one in the room," as Weis wisely puts it. "Trust is only as good as the level of comfort you've built with your business partners, and making every success look like a business success will build that trust."Follow everything from CIO.com on Twitter @CIOonline, on Facebook, and on Google +.