How can they "fix it for good"? Dust is dust and you and your camera are bathed in it. There is one solution to dust, get a camera with no openings or removable lens. Dust is not a repair issue the exact same way dirty windshields on new cars are not warranty issues. But many dealers will clean them for customers just to be nice. Learning to use the camera or to post process is much more of a learning curve than learning basic camera/lens maintenance. All sensors are dirty to some small extent but shooting at normal apertures results in few people seeing a problem. More users would notice a few spots if they shot at f/22, a point way beyond the onset of diffraction on a high density sensor. Ordinary dust is not a defect in a camera and if you think it is, there is no camera with interchangeable lenses, being shot at f/22 that will make you happy. Cleaning lasts as long as there is no dust in the environment, which means do not expect a cleaning to be the end of dust or fixing it for good.
Some time in the recent past, normal maintenance, for some people, has been redefined as a defect or the manufacturers fault. I am at a loss as to why that change has occurred but a DSLR might not be a good camera choice for those who believe pulling out a credit card at the store was the last active participation and responsibility they assume. It just would not occur to me that a car or camera manufacturer is responsible for the wear and tear or dirt I subject a car or camera to. Can someone explain where this strange notion of dirt being a defect came from? It did not exist as far as I recall 5 years ago. Is it only a North American phenomena, because I have not heard of it elsewhere. My GF read some of the posts, and while not a techie at all, she was puzzled by the same question. Even as picky as she can be, when she walks on the street with a new pair of high heels she would be happy to concede that if her shoes got dirty, it was her responsibility to clean them. She does just that more often than I clean my lenses or camera but I do it every time I go out on an event shoot, speeding 20 minutes cleaning and looking after my gear. Since I do not shoot at f/22, I obviously miss some noticing minor dust. I am also curious why diffraction that is a very real problem at f/22 is not a concern but a bit of dust is? Maybe I am just too old and logical to understand the thinking involved in that mental gymnastics. Stan St Petersburg Russia