Comment by proberts

There's no requirement that a green card holder spend 6 months in the U.S. during the year. You and your wife can and should travel freely. And you could live outside the U.S. for several years and still keep your green card. If you decide to move to Portugal for a period of time, for example, you should consult an attorney but the solution to protect your green card status (for at least 5 years) is to get a document called a reentry permit, which is easy to get.