Typical heat degradation on physical boards comes from continual expansion and contraction cycles that cause things to need to be reseated on the board.

This model has basically everything built into 1 piece, and it runs at a power throughput 7 or 8 times lower than your typical laptop. Heat is definitely not going to be what does this in over time.

Physical deprecation isn't what is going to impact life here, it's going to be depreciation. This is a first generation model that shows a lot of promise being put in one of their core business lines. Software compatibility will continually get better, but even by the spring, they will probably have a new class of chip with significantly better performance coming out. I'm not saying you should always wait for the next year's model, as I'm not one of those people. Just keep that in mind if you're thinking about a 5+ year haul, if you're prone to new tech envy, the next couple years will likely be a wild ride.