The most important part is the airing in the sun as UV is the most effective solution for hygienic bedding. Also if your worried about dust mites for allergies, then you only need to be using a mattress & pillow protector and these need to be washed every week.
Also if you sleep on a down pillow then this needs to also be washed regularly (perhaps every month) as the down breaks down into dust from the pressure of your head. This does not apply to the duvet unless you happen to sleep ontop of it and under it.
You can also just vacum your duvet, blankets and mattress every week to remove most dust mites.
I suffer from asthma and allergies so I'm rather full of nonsense with my bedding but I'm in no way a hygiene freak.