Dutchman, I'm sorry that you're having a problem with your microphone. But you certainly don't "have to" go through Redding Audio; you have a perfect right to send your equipment in for checkout or service without anyone else's say-so. It's just that you'll probably be astonished at how much FedEx and UPS charge for insured overseas air shipments nowadays, and the amount of time saved may not be as much as you expect. Redding Audio offers a service, which is to bundle the repairs that come in and split the cost of shipment among them all, as well as managing the paperwork and insurance. This is not done at a profit to themselves.
The round-trip time you were quoted is longer than usual, and I assume that the holidays are the main cause (plus Redding might have sent a bundle out fairly recently already). I know that Schoeps will be closed for the last full week of December; most likely they won't be at full strength until January 2nd or 3rd.
Air mail is certainly cheaper if you trust it, and you might save ten days or more since Schoeps would send the microphones back directly to you. However, you would have to arrange payment with them before they ship. Are you familiar with the German banking system? You don't just send money to whoever you owe it to--you send it to their bank. Sending a check and getting it cleared can take three weeks. And of course, until your microphone has been at least looked at, they can't tell you what the charges will be.
So unless you're able to make instant payments in Euros--like, if you have Internet access to a bank account over there--you will probably save less time than you expect, you will definitely pay more for shipment, and the arrangements will be more complicated. I use the Redding route myself, but my repairs are never urgent--none of my Schoeps stuff ever seems to break (he says, typing with his fingers crossed).
--best regards
Important P.S., added the next morning: I'm blissfully happy to answer questions like this if I happen to know the answers, but people: Situations like this one are why we need professional audio dealers, and why it's worth cultivating some kind of relationship with such people (normally just business, though I know that "full service" can have another meaning).
Anyway, I urge you all to purchase your good recording equipment from dealers who will be there if you have problems, and who can help you reason out what to do next, if not actually take care of the problem themselves. I'm not just talking about Schoeps here. Back when I was starting out, microphones were still all horse-drawn of course--but dealers knew who their customers were, knew their product, and had advice that was worth listening to. There still are such people but you may have to look for them. I'm saying that it's worth steering your business to them, to keep them in business and to let them help keep you going, too.