Still rolling on MBP 2011
Rolling on a 17inch MacBook Pro 2011 I did feel twinge of sadness when the machine could not upgrade to the latest OS. After replacing the CD-ROM with an SSD on day two of ownership and recently doubling the RAM to 16GB the system still copes well with research and development tasks. Replacing two motherboards ( one free under recall, one paid for) and putting in a new battery I expect to be using this one for a few years more. I waited for ages before looking at the latest shiny mac toy but would miss the big screen, traditional 3 * USB, external display port and wired ethernet but the firewire not so much.
Upgrading would also obsolete the Adobe CS5 and office that I regularly use but don't want to buy again from scratch. Despite it's high initial price and spendy repairs to get 9 years (and counting) service out of a laptop proves the benefits of repairability and upgradeability. Retail machine power exceeded most consumer needs in about 2010 and Intel have plateaued since. For my other desktops upgrading the GPU has and storage has kept them from needing a refresh.
Buying a new mouse/keyboard every few years make a desktop machine feel fresh again and is certainly cheaper / greener then swapping out the whole device.