I'm using a 17" 2010 at work with an i7, SSD upgrade, and 16Gb of RAM and its plenty fast still. At home I've got a 2010 Air that begs for more RAM yet still runs as well as when I bought it including 3+ hours of battery life depending on if I am surfing or writing. 2010-2012 was a high point in Mac laptops.
I'm hoping it will be good for 3 more years.