If it isn't a joke, it sounds vaguely mad, Hongyin!
Though I am by no means an expert, I would suggest strongly that another thing you definitely want to avoid getting on your sensor glass is moisture. The 'bathroom' scenario sounds like it would be a dead cert for that.
I have found 'dust' spot problems with my sensor that are not in fact dust. They look more like the spots left by droplets of moisture on the glass, or marks created by a bit of something long gone, but the mark remains, partly due to moisture.
My view is that dust spots are inevitable for a DSLR that is in use, unless you are using a fixed focus lens that you never remove. As soon as you take a lens off you allow the air - with all that that contains - dust, moisture droplets and all - to get in to the body. Also, any use of a zoom sucks in air every time it is zoomed in and out, as it is not completely air tight. The only solution is to clean the sensor glass - scary though that is initially.
But I do agree with the point made earlier that a sensor that looks dreadful at f22 can look fine at f8, so that is a key factor. If you have the lens quality to do it, and depth of field is not key to your image, a wider aperture helps disguise the problem.