I've never sheared any of my labs, but every summer I give my setters and spaniel a close shave. I do it mainly to cut down on the burdock, beggar's lice and other stickers that get in their coats, but it also helps keep them cooler and I have never noticed any problems with skeeters, deerflies, etc. As for my labs, I give them regular access to the pond and ensure that they have shade in their kennel. This is a tough time of year to have a black coat!