Crazy, in my entire career I've never been involved in a redesign that didn't involve the entire layout but only changed some colors, paddings and drop shadows.
Definitely done it a bunch of times. Marketing comes out with some new web font crap they want and we need to go adjust everything. Flat face buttons become popular so we get rid of the pseudo 3d ones. They want to launch a new webstore but dont want to redesign, lets just steal one we have and reskin it a bit.