Inzax, I do not believe you are doing anything wrong. I have only 11,000 on a 2006 6.0L diesel. I have been to the dealer many times for oil leaks. Mine started leaking at 1,100 miles and I bought it new!! I think (knock on wood) they have got all of them now. I also do not pull a trailer, or abuse the truck in anyway. Oil leaks are just something that happen to a lot of owners of 6.0 L's from what I have read.
Are you under warranty? 100$ Deductible?
Let me know what the dealer does to your truck. I want to keep on this subject. It really has bugged me a lot. I crawl under my truck each week with a spot light and UV light. There is dye in my oil in case it starts leaking again. Gary A.