UV light from the sun is probably the biggest contributor to windshield wiper deterioration. Maybe the glass scratcher side of a snow brush, but who uses that?!?
Sunlight, freezing and thawing, and the fine sand from those darn gravel quarries. Popular wisdom around here says to replace wipers annually. I replace them when they leave streaks too often. For some of us, the ice scraper is a standard item to be in the car at all times. I also find that the California Blade is helpful for clearing rain and dew.