My back and shoulders have been hurting more and more (I'm only 27!) and it took me way too long to accept that slouching over my laptop was causing it.

Putting my laptop on a pile of books and using an external keyboard and mouse made a HUGE difference and my posture has improved significantly after just a couple of months.

I recently bought a Roost laptop stand which is great for travel and looks like spy gear but it is a bit pricey and a stack of books does the job too.