From my experience with Amex the Hilton HHonors card and Preferred Rewards green card I got initially both had a 2 year expiration date. When the cards expired both new cards had a 3 year expiration date. On my Blue card, the expiration date was 4 years from day one and hasn't come up for renewal yet. On my starwood card the card was initially given with a 3 year expiration date. And my fidelity gold card also had a 2 year expiration date. So my guess is that Amex usually issues their charge cards and some credit cards with 2 year expiration date and then ups them all to 3 years except the blue which because of the chip had a 4 year expiration.