It's probably been around three years since I last had my K-1 sensor cleaned, and for the most part it hasn't been much of a bother to remove the occasional sensor spot off any photos.
However, it got monumentally awful over the last few weeks, to the point where I gladly took it in to the local shop. I really don't know how it got to that point either, but one day a line of dots appeared on the photos, like a centipede had marched across the sensor. I think my rocket blower may have somehow been responsible, as the previous day I ( successfully ) dislodged and removed a larger dust particle that was causing a very dark spot on the photos. I was careful not to allow the blower tip make contact with the sensor, but it's possible it sprayed some debris across the sensor in a line. It doesn't help that I shoot my beach composites usually stopped down to f20 or f22 to get the depth of field I need for longer focal lengths, which I would expect would make things worse?
I got the camera back and went out for another shoot as was very surprised to find that the resulting photos were spotless! I thought much of the mess was from dust on or in the lens, but nearly all of it must have been the sensor! $60 well spent, I'd say, judging by the collection of Spot Removals in Lightroom on the photo ( vertical pano composite, one photo for the sky, three photos merged for foreground ),
I'm sure others have seen much worse