My father is American, approaching 80 years of age, and has been living away from Brazil (in the U.S.) for the last 25 years.  Even so every few English sentences he pauses to find the English word he's looking for, often saying the Portuguese word first.  Lately he's just been saying the Portuguese word without bothering to translate, meaning I end up translating a lot of words/concepts on the side when he's talking to my American wife.<p>My father spent the "core" of his adult life in Brazil and dealt with every-day concerns in Portuguese.  He traveled a lot away from his English-speaking family and was immersed much of the time.  He practiced his domain expertise (soul-saving) in Portuguese.  In most matters he's just more comfortable in Portuguese and Spanish, and it certainly shows when he speaks English.