I'm in the UK and find Kodachrome has been taking about 14 days to come back ever since the system of sending to Dwaynes via Kodak Lausanne came into force. Perhaps one or two days longer if sent at a w/e. My last one, received last Tuesday, unusually took just over three weeks, but I put that down to the postal workers strikes...other mail was a day-or-two delayed.
"Touch-wood-and-cross-fingers" :rolleyes: , I've never lost a film sent via Switzerland, but I do send films individually, rather then together in a batch
(better lose one film than several if a packet does go astray?).
I don't usually worry too much about Kodachrome's long trip, but on one occasion earlier this year where I knew my pics would have particular sentimental value (a special one-off family holiday) I deliberately shot a mix of K64 and E6. (Not sure if I was more worried about lost Kodachrome or cr*ppy UK E6 "professional" labs, but that's another story. )
Hope your four-week film arrives soon and that it's just down to the UK postal issues...let us know what happens.