What are some things that I can do to increase the lifespan of my laptop?

Sometimes laptops overheat when powered on and sitting in a bag. Don't place laptop on pillows and soft surfaces, get one of those bean pads with the flat surface on top. Hard drives have a life span of some thousands of hours but every time you leave it running it diminishes a tad bit. NEVER USE HIBERNATION MODE! I worked as a IT assistant all last year and I dunno how many time we had to trouble shoot people's laptops because they let it go into hibernation mode (assuming you have windows). If you are always charging the battery the lifespan goes down. I'd suggest if you know your gonna be sitting in the same spot for a while either use it with the battery out or let it run down then charge it up. Also get a air compressor that can blow air at a high psi so you can clean the fans and keep it clean of dust.

Jam it back in, in the dark.