Be cautious, I had a close friend have their Green Card seized while crossing the border back from Canada into the United States, even though he had documented evidence that he had spent 95% of the previous three years in the United States. He was a consultant, and traveled a lot, but thought he would hang out in Vancouver, BC for a while. Even though he only returned to Vancouver for a few days at a time, before going on the next engagement, and all engagements were in the United States, with a US employer, (And he was a Stanford Graduate) - they seized his GreenCard because his household goods (Mattress/clothing), had left the country more than a couple years ago, and used that as evidence of being away from the United States.

Lesson learned - Sometimes the border staff gets caught up on stupid technicalities. Be aware of them, and don't use common sense.