Can you just return a phone within 30 days, buy a new one...then repeat?

Like, bought a new phone (Nexus S) at retail price at best buy. Can I just return it within 30 days, then buy a new one, either a Nexus S again, or any other phone...then in 30 days, return again and buy again? That way, so I can always be able to get the newest phone available?