Hard shell long term use question?

I should be getting my rMBP later today. I had a question I hope you more experienced folks could answer for me.
If I use a hard shell case cover that snaps on the MBP does it scratch the MacBook after long term use? I read somewhere that you should removed it weekly an clean it so grit does not build up and scratch your $3700 laptop.
True?

 

You are correct. If you do not remove the cover about once a week you can actually get sand and grit in between the cover and the macbook which will move around and scratch up your macbook really badly.

My wife had a hard shell case for her 13" macbook pro and she kept the case on for like 6 months. When she took it off after that 6 months her macbook was all scratched up.

I would personally recommend either getting one of those skins that doesn't use adhesive or going without any cover at all. I have never covered any of my MacBooks and I have never had issues with them getting scratched.

 

Correct, the surface (Aluminium Oxide) is already hard enough.