I think they have an issue actually in that you need more than a grape-pickers' permit now to change the licence and thus they don't check as hard as to how long you've been in the country.

The best working excuse I've heard is to say to them that you never changed the licence because you did not have a car and now you're just about to get one.

Frankly, your ability does not diminish on day 366 of your time in Switzerland....