Curious how often you guys feel the need to clean your CCDs? I've found that after about 800-1000 shots and probably 8-9 lens changes I need to clean it. I'm not sure if this is because I've just never cleaned it real well? I just use the blower with the soft bristles and it does ok. For those of you with self-cleaning ccds how often do you have to go in and really clean it? Because you still get "welded" dust right?