years limit offer because you explain in this way: this is just for the PostDoctor fellowship position, they may transfer you to other position after two years. Now a lot of companies, like Samsung and Microsoft, they have contract-to-permanent opening. You can ask your future manager to write a letter to explain it if ref requested. actually two years is pretty long contract. Second, you report to USCIS your move, and if you just file AR-11 by paper, the IO may never know you move because in general they process AR-11 very slow, maybe 2 or 3 years later.