I think most people whio get coated dogs VASTLY underestimate the amount of thorough grooming the dog will need :( they brush the top coat and think the whole dog has been done, they then get the dog clipped as it 'gets hot' If more people were honest with themselves about the grooming they do then their dogs wouldn't need clipping.
I had to groom a sheltie a while back and it took me 3 days to get all of the dead coat out - 4 carrier bags full!! from a sheltie!! This was a dog I had tried to persuade the owner not to have as he wasn't physically capable of the level of grooming which a sheltie requires or the exercise :rolleyes: a shorter coated dog would have been much easier for him and kinder to the dog but he loved the 'look' of the breed :rolleyes:
As far as heat is concerned, I used to own an Afghan Cross (Black) and groomed him daily, with a thorough grooming for 2-3 hours every week. In summer I reduced his undercoat to almost nothing. One summer, back in the 90's, there were temperatures of high 80/90's and we were on holiday with him

he was the only one of us who didn't flake out in the heat and he was about 10 at the time. I put it down to having no undercoat and not encouraging him to run about (none of us felt like moving much)