The dogs well-being and happiness comes first.
It is my opinion that with older dogs in the summer they really do appreciate a short cut, my Ben who has the most beautiful coat was short cut last July for the first time and the difference in his activity and mood was very noticeable. He will be getting the same in a few weeks time.
I do not believe that long hair protects from heat as others sometimes say.
We trim slippers, potty area, and a bit off the feathers. He's very low to the ground and with the morning dew he's soaked through by his first potty. I haven't touched his ears, but I'm sure we will keep a puppy cut going.