Hi Mokona! I was in your beautiful country two months ago, though down in Andalusia so I didn't see you.

But what a great place to eat and drink!
Can I ask how do you change your lenses? I make sure the camera is facing downwards when I take off a lens, so gravity works to keep crap out. And I have the second lens ready with the cap loose, so I can just pick it up and put it on in a few seconds. Though I will admit that sometimes I fumble a bit.
I also have sensor shake turned on, so I get the thunk each time I power up the camera.
Doing this with my K20D I rarely need to clean the sensor. When I do I use the Arctic Butterfly, which is an electrostatic brush. A few sweeps seems to work to get any little dust off the sensor. (They have several models but just buy the cheapest one -- they are all fundamentally the same.)
This would be an unfortunate reason to give up using your lovely primes.