Hi SusiC,
I have a English Lab and have gone through the same exact thing with her. She had to go to the vets at least every two to three months and oh what that cost us, and the suffering she went through. I switched her from the regular food she was on, which was holistic, but contained grains. The important thing to tell you is that I started her on "grainless" food. She has not had one single ear infection since, and it has been a good two years.
There are several brands to choose from at your local pet store. Ours is Pet Depot or Petco. Also, your local farm feed stores will have them. Yes, they are higher priced, but they are far better quality and so much healthier. God didn't design your dog to eat grain.
I sure hope this helps your problem.
Gloryb