The U.S. Navy learned during the Afghanistan and Iraq campaigns that the post Vietnam custom of sending carrier task forces on regular six month cruises (followed by 6-12 months in port, with some local training cruises) did not allow for maximum use of fleet resources. Both Afghanistan and Iraq required a maximum effort from the navy, with some carriers staying out longer than six months and others that were not fully trained, being sent out. For Afghanistan, it was because we had no nearby land bases. For Iraq, we didn't have enough nearby land bases. Early on, it was proposed that the six month tour be dumped, to be replaced with a more flexible system. This would mean ships would normally spend most of their time in, and around their home ports. Ships would only be pulled out of service when they needed major work in a shipyard. The navy has found that modern warships, and well trained crews, can keep the ships in excellent shape for a lot longer than in the past. 

An analysis of overseas crises in the past three decades has revealed that it's rare for a situation to come out of nowhere and require the immediate attention of a navy carrier and amphibious task force. In nearly all cases, the situation would warm up gradually, giving carrier task forces time to steam from their home ports to the hit spot. And if a situation became really dramatic, the new, more flexible system would allow the navy to "surge" more carriers and marines to the distant location. Moreover, these sailors and marines would not already be worn down by months at sea, and be faced with many more months off a hostile shore, until the situation was resolved. A carrier at sea is a dangerous place to see, and carrier crews suffer more injuries and deaths while at sea than when at port. Marines would much rather prefer training ashore than spending months on a cramped amphibious ship. So it looks like the three decade rule of the "six month cruise" is about to enter the history books.