Using them on dry roads kills them I think, especially if it's warmer out.
Put them on when you see a solid stretch of cold weather (and snow of course) and take them off when you don't see much more snow. In late winter (because the cold weather lasts well after the sun has reached higher in the sky) the sun melts the snow during the day, so you don't really need the snows even though it's still cool out. You learn over time when they are needed on average, plus watch the forecast and wait for the first big storms and cold weather.
My prior car's Firestones (Winterforce - can't recall if that's the new name or old model) lasted most of the car's 15 year life (99 Contour). One winter we only got 50" or so (pretty much a record here) and under 100" another year, I kept the summers on those 2 years.
I replaced 2 of them last winter, partly because one leaked, but the other 2 are still from 1999. I only put ~3k miles on them each year, and being a light car, they did no wear quickly. Roads are often wet here - they salt the heck out of the roads when we get under an inch of snow - arg!!!