Can you become tolerant to patanol (olopatadine) allergy eye-drops?

No: Patanol (olopatadine) doesn't become less effective with use and tolerance doesn't develop. No medications used to treat allergies develop tolerance. This only occurs with a small number of meds, usually those affecting nervous system, e.g. Pain killers, sedatives, sleeping pills, etc. Probably you are being exposed to more pollen, dust, etc. And your symptoms are worse.