D600 dust issue, are you not worried that something maybe failing inside the camera?

I am a professional Photographer and I have tried 3 copies of the D600, the first seemed fine until I read about the dust issue. I then checked and returned it as it was displaying a large number of dust spots on the top left of the image visible at f8/f11.

I waited another month before I tried again, this time the 2 copies I tried never left the store as the dust spots were almost evident as soon as we started taking photos.

If you are a professional would you risk turning up at an event and even though you've blown the sensor to remove the dust every 100 or so shots, wouldn't you be curious as to where it's all coming from?

What if the shutter was slowly shredding, and what other problem could occur?

Would you buy a car and be happy if the tyres starting shredding as soon as you left the shop, is this  acceptable?

I've read about people saying, "just blow off the dust, it disappears after 3000 shots"Are these people working for Nikon?

I thought a high megapixel FF body would be an asset to me for certain tasks, but I think my best option is a D4, the D600/800 cameras don't seemed to be aimed at the professional photographers,the D3X was, how about a D4s with 24mp, that would surely be the solution.

Please don't take offence to anything I've written if you are a dedicated Nikon user who thinks I am slandering what they live their whole life for, I'm not. I'm just asking a question.

I must admit my D3 and D3s combination does not really need an upgrade, I just thought it would be great for large group shots and taks that require an large output.

I do love the image quality of the D600 as I said in an earlier post, it's just the reliability issue that's holding me back.

Cheers

Rob