Maybe if you're doing video rendering or music production or something?
I'm running an early 2011 MBP and it's still a fully capable machine. Like the 2012, I have been able to customise it by adding more RAM, rolling my own fusion drive and just recently replacing the battery. Doing that I think it's got another few years left in it for what I need it to do.
I used to pine for the new MBP models when they came out, but stopped when they started losing ports and user upgradability. It'd now take more than a retina screen to get me to upgrade to a new model. I'd be more likely to buy a 2012 model if this one broke.