For the U.S. Navy, the Good Old Days of the post-Cold War period are gone. In the early 1990s, with the Cold War over, and the mighty Soviet fleet rapidly falling apart, only about 25 percent of American warships were at sea at any one time. But since September 11, 2001, there's been a lot more to do, and about half the fleet is at sea at any one time. Most of this has to do with counter-terrorism operations, and support of operations in the Persian Gulf and the Indian Ocean, and keeping an eye on the growing Chinese naval forces.
To make this possible, the navy has changed the way it goes to sea. Gone are the regular, clockwork, six month deployments of carrier and amphibious task forces. Now these units deploy for shorter periods, giving the crews more time in port, and more reason to stay in the navy. Too many long deployments, and sailors have to choose between the navy and family, and the navy usually loses that one.
The U.S. Navy still spends more time at sea than any other, thus maintaining skills that are second to none. But that requires billions of dollars a year for fuel and spare parts, not to mention the months ships must spend getting major maintenance, after years at sea. If the money doesn't keep coming for this, the U.S. Navy will end up like the Soviet fleet, rotting away from lack of maintenance and training.