Can we be served with a 3-day notice to quit simply because the rent has been paid about 15 days late for several months?

We have lived in a single family home for 15yrs. And have always paid rent each month NEVER have we gone a month without payment, although we have paid late on several occasions. Now, the owners have told the property manager to issue us a notice to pay or quit if we don’t pay within the first 5 days of next month. Is this legal? Aren’t they still required to give us a 60 day notice since we are month-to-month? The prop manager feels the owners may be receiving advice from others as they consistently raised the rent over the last few years seemingly to match market rents; ours is below market rate. We have appreciated their patience over the years and all we want is legal consideration before they kick us out just because now they exhausted their patience with us.