Step 11 = Put pillow protectors on all pillows.
Next time you wash your pillowcases, have a look at the state of the pillows inside them. If they are tea-stained, drool-marked and a bit stinky then it is time to wash the pillows themselves at 60 C to kill bacteria and dust mites (if the pillows will tolerate 60 C - please do check the washing label). Or, if not, then wash the pillows, with Napisan added, at 40 C and dry outside in bright sunlight to assist dust mite destruction. Or you could splash out and buy new pillows.
Now, I'm sure that's enough faff (or expense) to make you want to protect your pillows indefinitely. So invest in enough waterproof, zipped pillow protectors (washable at 60 C) to cover all of your nice, clean pillows. Plus buy spare sets of pillow protectors as they don't dry quickly, being as they are waterproof (they need turning the other way out half way through line-drying), or buy ones that can be tumble dried, like those mentioned below. Carefully check the reviews online before investing, as some waterproof pillow protectors can be sweaty or noisy to sleep on.
After trial and error, I favour the ' 100% cotton, LIQUID RESISTANT, pillow protectors with zipper' sold by 'Bid Buy Direct' on Amazon, at around £3.50 per protector (they come in a pack of 4) - make sure you buy the LIQUID RESISTANT ones from Bid Buy Direct (as they have other inferior types too), the 'liquid resisitant' ones may not technically be waterproof but they have kept our pillows looking like new, many other Amazon reviewers are happy with them too it seems.