How thin boards will hold out for regular use? No one knows. But Exocet did already last year have the waveline Surf II with width to volume ratios very similar to the SB Quad of this year.
Have they held together? That should be some kind of indicator.
And Exocet has launched another thinnish line of waveboard, the 3X, for this season and is keeping the Surf II unchanged. It cannot have been too bad.