I kept mine going for as long as i could until it was just blatantly too underpowered. I upgraded to the 15in retina(magsafe style, not the new one) and i'm still grumpy about the screen size downgrade.

Where is the 4k 17in MBP? The old one was 1920x1200, it would be a perfectly obvious upgrade

This! I loved my old lunch tray.

+1 My 2006 17" MBP is still used daily (Ironically I'm writing this on an XPS 15 running Fedora 25)