How long can I use Zaditor eyedrops? Weeks, months, indefinately?

I realize this answer is very, very late ... but may help someone in future.

Zaditor (ketotifen ophthalmic) is an antihistamine that inhibits the body's release of a chemical called histamine. Histamine can produce allergy symptoms such as sneezing, runny nose, and watery eyes.
Ketotifen ophthalmic is used to treat itching of the eyes caused by allergy to dust, pollen, animals, or other allergens.

You can use ketotifen long term. You can use it for months ... it might not be necessary to use it indefinitely. Only use it when you have allergic reactions.

https://www.drugs.com/mtm/zaditor.html