I'm going to probably say this until they manage to make laptops thermally efficient which given that they haven't yet means a very long time, but a laptop cooling pad/fan is probably one of the best things you can get to extend your laptop's life. Also, if your laptop is the same OS as the previous one/you want to use the same OS, you can just image your current hard drive and boot from the image on your new computer.

The move does kind of make sense from a story POV, since in that chapter of the movie (aside from dealing with Smaug) the big event that they run towards is the battle of the five armies, and Thorin's death and etc.