By saying I get a new duvet every few months I just meant I switch from summer to winter duvet, so in 6 months or so I will buy a winter duvet and put the summer one in the cupboard. Sorry I should have been more clear in my op
And in the summer you take the summer duvet out of the cupboard, wash the winter duvet and put that in the cupboard for next season? So it is worth spending money on them, because you'll be keeping them for years, surely?
You need several things:
Washable pillow protectors for DH and medical advice about the nose bleeds.
Seasonal appropriate duvets of quality appropriate to your budget, some shopping around etc should allow you to get the best combination of quality and price.
Somewhat randomly, I found the Silentnight hotel pillows mentioned above for £9 a pair in a local Poundstretcher when I was looking to see if they had the things I couldn't do without when I CBA joining the massive queue for the Tesco on the same retail park.
If you get synthetic bedding, a washing machine with a big drum then you can wash your duvet any time you like for minimal cost, so you aren't faced with paying laundrette prices so you replace rather than wash and reuse.
I realise if you don't already have said washing machine, this will have to wait until you need to buy a washing machine, but being able to wash a king size duvet at home any time you like is not quite life changing, but a massive convenience and money saver.