I've had my MB-D11 grip for 2+ years and sent it back to Nikon after 6 months because the rubber was coming loose from the lower left part of the bottom of the grip. They fixed it under warranty and a year later, it started happenening again. I had a Nikon grip on my D100 for 8 years with no issues. When I got my D600, I bought the Pixel grip for $95 and so far (2 months), it works fine.
Jim Singler D600/D7K with a bunch of lenses and other assorted stuff