The definitions from Apple's Vintage and Obsolete products page give an idea of device longevity. The harder you work your machine, the sooner a component is likely to stop working.

Someone who only uses their Mac for occasional web browsing can likely get away with using the same machine for longer than someone who runs their computer all day and does high-intensity tasks like video editing. There isn't an exact number you can put on a Mac's lifespan, as it depends on a variety of factors. OS X can off-load some functions to a video card in this manner but I don't think this will help with running games.Whether you're taking stock of your old machine or thinking about the value of a new purchase, you might wonder how long MacBooks and other Mac models last. Unfortunately OS X cannot currently fully utilise a video card via an expansion box in this manner, Windows running on the same Mac via Boot Camp could. However theoretically with regards to the video chip you can buy a Thunderbolt to PCI expansion box, fit a standard PCIe video card in that expansion box and get a far more powerful video chip - even one in theory powerful enough to drive an Occulus Rift. With regards to the video chip, again as this is part of the logic board and cannot be swapped the answer is realistically the same. The effective option for upgrading to a faster CPU is to sell your existing laptop and buy a newer faster model. Furthermore Apple do not have a scheme whereby you can trade-in your existing logic board and get a new one with (slightly) faster chips.

The CPU and video chip are soldered to the main logic board of your MacBook, they therefore cannot be swapped out.

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