Mine's one of the first run, and it's never broken. If you know how to maintain a PC, you shouldn't have a problem with a 360.
80% of the break because the users threat it like stuff or place it somewhere awkward (like on the floor where anyone could stand on for no reason).
5% broke because they bought one of the first released that were crappy made.
15% just got bad luck on their side and it broke for no reason (try to open your xbox and look for yourself or resent it and get it repaired).