Hi Jacob –
Chronic otitis in dogs can have numerous causes – many of which are secondary (meaning the otitis is in fact a symptom of another underlying issue).
If you’ve been battling ear infections for as long as you have I’m sure your vet has already looked into this, but just in case, has a scraping from the ear been examined to check for yeast? Malassezia is a fairly common type of yeast that can infect the ears.
Has your dog’s thyroid been checked (especially would recommend having this done if the dog is overweight). Hypothyroidism can predispose dogs to chronic otitis.
Have you tried a grain-free diet? If not – I’d recommend trying a grain-free diet with a novel protein source (think rabbit, buffalo, kangaroo, etc. – something your dog hasn’t eaten before). Keep her on this for a couple months and see if things clear up.
Supplementing with multi-strain non-dairy probiotics, enzymes and coconut oil probably wouldn’t hurt either.
This is by no means an exhaustive list of what could be causing the otitis, however it may give you a few avenues to explore as far as getting to the root of the problem.
