nokia plastic covers

[jjlim15]

I am currently using the nokia 6100 along with a full clear plastic cover. Today i heard from a salesman at a cellular store that these covers are actually bad for the phone. He said somewhere along the line that the plastic being unable to transmit heat and therefore may actually damage the phone. I do not know if this is true. I'm wondering if anyone has heard anything similiar to this or know of any problems resulting from such a cover. I however doubt that a plastic cover may cause problems to a phone.

[markchee]

You tell the saleman,both are plastic what to do with heat?