Thanks for reply. A DC33 I have does say it can be washed up to 10 times every 3 months, indicating 2.5 years of life from the HEPA. So, this is at least better than many others.
I was aware that the HEPA filters on the DC14 are simple replaced, but these seem to be a more popular machine than the DC33, perhaps as they are older and more reliable, and the newer DC33 has changed diameter of the wand, and older fitments no longer attach. Whatever, thanks for the reply, and yes, advice on the DC41 would be welcome, as it seems to me like a card "comb", and I do not think that lends itself to washing quite so easily!