While the official reason is to save money, the new U.S. Air Force policy of keeping troops at a base for at least four years, versus the former three year minimum, is also a major morale boost. Since World War II, the American military developed regulations, procedures and customs that result in moving people around frequently. Two years ago, when the army introduced a similar policy, several hundred "obstacles" (regulations, procedures and customs) to the new approach were identified , and a lot of effort will have to go into working through them. The air force will have the same problem.
The army approach was more ambitious, and they called it "homesteading". This policy keeps a soldier at one base for 6-7 years. Before that, most troops (air force and army) get moved around every two or three years. This is very unpopular with wives and children, and over half the troops are now married (compared to 25 percent two decades ago). Since World War II, "homesteading" had been a dirty word, as it implied that someone (usually a senior NCO) had pulled strings in order to stay at one base for up to a decade. The implication was that the guy must have been up to no good. Times, and attitudes, have changed.
One thing that hasn't changed is the way "unaccompanied" (by family) tours of duty. In the army, the most common one is Korea, where for over half a century, troops have been sent there for 13 months of service. The air force sends troops on these hardship tours for shorter periods, usually six months. This was good for morale, even though air force personnel went overseas more frequently as a result. But the real morale booster is being able to keep families in one place longer. And it saves money too. The army and air force have concluded that careers and training will not be hurt by the new policy. In the past, it was felt that the frequent moves were good for both. For half a century, the brass ignored the downside of these frequent transfers. Now they have paid attention, and found that the frequent transfer policy was hurting more than it was helping.