I want to buy a MacBook for extremely basic use with the sole priority being ongoing tech support from apple. I would also like to save money by being a refurbished model. I see some reasonably priced MacBooks online that would undoubtedly perform most of the web-based office stuff I need, but I am wary of buying an older model that Apple will stop supporting soon. How long does Apple support this type of thing? What's the oldest model year I can buy that will continue to be supported for 3-4 years?