Posted: 05/09/2014 at 09:03
It all depends on what sort of blight, Sue. "Blight" has become a generic term for any sort of fungal disease. There are two true Blights - Early and Late. Early Blight is manageable with good housekeeping - removing affected leaves as soon as symptoms appear, etc. The plant will go on producing. With good housekeeping, cold weather will stop the plant before EB does.
Late Blight is a different matter. It can and will kill a plant within a week.
There are at least half a dozen other fungal and viral diseases that are loosely called "Blight". Few of them are as destructive as Late Blight.
Blight resistance only means that a plant is bred to cope better with certain fungal diseases than a non-resistant variety. It doesn't mean the plant won't develop disease. No tomato plant will resist Late Blight.