psssstttt.... it's a myth.... I've posted it before, I'll post it again... for your reading pleasure and to comfort your soul - it's in German but you can get it:

Quote Originally Posted by alpinerabbit View Post


http://www.tour-magazin.de/?p=173

in almost every instance, the stress on the downtube (TU), chainstay (BK), and seatstay (BS) is higher on the road than on the trainer.
The three instances tested are at low intensity, high intensity, and standing up.
My LBS said in the winter, just leave the trainer skewer in, and it will take the occasional road ride when the weather is fine.

(Well this season I have a MTB to take outside if I feel like it).