Tim
This link to
PPL/IR Europe contains a wealth of information.
Not really sure how many folk let these ratings lapse? I suppose eventually all ratings lapse but it would be a big pity to let it lapse within six years of gaining it - otherwise you would have to do it all over again. This would be a bad thing and not the way of dam fine airman!
It's a mute point - but if you have an IMC rating this can be revalidated automatically with your IRR. Sort of interesting little freebie.