cross country rego
 

i have German export plates valid for three months and am planning to cross europe middle east asia do i need the export plates to be valid for the whole time i.e do i need to cancel current three month plates and apply for six months, the planned length of my trip.

I'm afraid you could be in for big trouble. I have never seen these papers, but I guess the expiry date is clearly marked on then. It is definitely marked in a big red field on the plate itself. I don't know whether it is possible to get the validity changed. Also, there are countries that will not let you enter with these.

I strongly suggest you contact the ADAC head office for advice. You will need to do that anyway for your carnet.