The deportation thing was explained to us like this. I found an article that explains it better than I did:

When is Permanent Residence Considered Abandoned?

You might have heard rumors that you must enter the U.S. once a year to keep your green card, or spend a certain amount of time in the United States each year. Those rumors are largely false.

They’re probably based on the fact that being away from the U.S. for longer than six months will raise suspicion and questions, and being away for more than a year guarantees that you will have to attend an Immigration Court hearing before you can reclaim your U.S. residency and green card.

But the bottom line is that that if you ever leave with the intention of making some other country your permanent home, you give up your U.S. residency when you go.