Pillowcases are one thing, toss them in with the rest of the linens and be done with it. Pillows on the other hand require special care to save them from a fate of mildewed lumpiness.
You can do some things to extend the time between laundering like changing your pillow case frequently and keeping a pillow protector on the actual pillow, but eventually anything that spends as much time close to your body as a pillow will need to be properly laundered. How frequently? They weigh in on pillow care at the home-centric blog Re-Nest:
It's a good idea to wash a pillow every year or so. mum used to take them to the dry cleaner, where the stuffing would be taken out, bathed in chemicals, and then put in a fresh, new case. But we try to avoid dry cleaning in general and it seems like an especially bad idea to put all those chemicals right next to your head every night. So, how do you wash a pillow if you're not going to dry clean it?
They go on to share a simple process involving the hottest water your washer can provide, to kill off dust mites, and a gentle detergent. Check out the full article for a point by point run down on how to launder your pillow and, most importantly, how to properly dry it.
How to Wash a Pillow [Re-Nest]