20D and dust spots

Dust seems to be a problem.

I noticed a piece of fluff on the viewfinder today. Rather than let it
migrate to the sensor I *think* I managed to remove it.

This prompted me to try the sensor dust test (stop down to f22 and shoot the
sky out of focus. Sure enough there are a couple of faint spots, so I guess
changing from film to digital won't mean I will be giving up using the clone
stamp any time soon.

What I find disturbing is this is a brand new camera for xmas, I only have
one EF lens which has been mounted exactly twice, once on delivery and once
on xmas day. The camera has only been used in doors apart from a short stint
(mostly because I have been fixing my central heating).

If this is the amount of dust intrusion at this point what are things going
to be like after changing lenses in windy conditions a few times?

I know the 20D is not a pro camera so I was not expecting the mount to be
dust proof, but this seems to be an issue. Is this a particular problem with
the cheap 18-55mm kit lens or can I expect the same problem with any lenses?

I was planning to get mostly prime lenses like my old system but now I
wonder if I should consider zooms just to reduce the number of lens
mountings....

Can some of the more experienced DSLR users please indicate how much of an
operational issue sensor dust is and what precautions they take.

cheers

Lester