My personal belief is that since they are made more fragile (I believe it's intentional), you risk the contact tearing while in your eye or not keeping the shape which could maybe cause a deformation to your cornea/eye(?) if used for a prolong time. I only think this because I always swam with my 2 week disposables in and my eye doctor got 'angry' when he saw my contacts were a little deformed from water exposure.