splitters
n. A family that splits their time between two or more houses.
Examples
2006
Enabled by cheap airfares, flexible work schedules and technology like cellphones, BlackBerrys and the Internet, a growing number of people are shuttling between two or more homes, blurring the age-old distinction between the primary and the vacation home.

Unlike previous generations, these "splitters" do not think of themselves as living and working in one place and relaxing in another. On the contrary, they come and go as they please, making friends and doing business in places hundreds, even thousands, of miles apart.
—Motoko Rich, “Double Nesters,” The New York Times, January 19, 2006
2005
Most folks are familiar with the term "snowbirds," a not-always-favorable appellation applied to Northerners who head south to their second homes before the harsh winter weather sets in. But now comes a new term, "splitters."

Coined by Florida-based developer WCI, splitters are vacation-property owners who visit their second — and sometimes even third — residences more than once a year.
—Lew Sichelman, “Meet the Splitters,” Chicago Tribune, December 25, 2005
2005 (earliest)
Here's the latest group to keep track of: splitters. These are people of any age who split their time between two or more homes, traveling for play or work or to connect with family.
—Judy Stark, “'Splitters' could impact Florida,” St. Petersburg Times, June 25, 2005