For RAM considerations I've usually recommended people get the minimal from Apple and then upgrade at a later date to save money however, for some of Apple's systems such as the MacBook Air and Retina MacBook Pro this is not possible, so purchasing the ones with the most built-in RAM is recommended. While for the most part these should be relatively comparable, the faster you go and the more capacity you give the system the longer you will be able to use it before you need to upgrade. Apple periodically updates its maximum RAM offerings. Apple offers a number of configure-to-order details including RAM capacity, processor speeds and types, and hard-drive size. Of the considerations for ensuring a long-lasting Mac, the first begins before you even purchase it where you are offered options to configure your system. While peripherals like the keyboard and mouse can be replaced, it may be harder to do so for the components in the machine. The first part of your Mac is the physical machine, which includes the logic boards and controllers, screen, keyboard, mouse, and other similar components. In most cases these will only have a little (if any) effect on the system but may help keep the system running longer and without problems or capacity limitations. There are many ways your Mac can get damaged, become outdated, or otherwise experience greater wear and tear from use that can shorten its lifespan. Regardless of whether you purchase it new, refurbished, or used, your Mac is likely a sizable investment that you might wish to keep running for as long as possible, not only because of the cost factor but also because of the time and effort it would take to migrate your data and workflow to a new system (even though Apple has made the latter quite easy if you have proper backups).

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