Hello, my name is***** and I have over 20 years of experience as a veterinarian.
I understand that your pup suffers from chronic ear infections in one ear that the use of Zymox Otic seems to treat nicely.
There are two types of Zymox Otic, both have components that change the pH of the ear and help loosen and remove wax, which makes the ear environment inhospitable for some infectious agents.
The type with hydrocortisone also has a steroid which will reduce inflammation and itchiness and is likely to help with allergic based ear inflammation. Using cortisone for extended periods of time can predispose to secondary infections and changes the integrity of the normal skin, as well as suppressing the adrenal gland and predisposing to diabetes developing. However topically applied cortisone is not absorbed in large amounts systemically, so would be less dangerous than systemic use from oral medication. So we need to be careful with these products, but we can use them long term if needed, just try to use them as little as possible to still achieve control.
If you are using the product without hydrocortisone then that is fine to use consistently long term.
If you are using the product with hydrocortisone try to use it as infrequently as possible, yet still enough to control the symptoms.
If you have any further questions please let me know.