I ran Blizzaks for years and they are excellent for light winter use, great in snow and wet roads. I never got more than 2 winters out of the outer traction layer. You can run them in the summer if you want, but you'll wear off the winter traction layer pretty quick.
I now use studs exclusively on the east side. There are often black ice patches on the east side roads in the winter, even in the west side foothills like the North Santiam Canyon upstream of Detroit.
I've come to believe that new or first year studs are the best, hands down. There is no substitute for sharp carbide edges dug into the ice, especially with soft ice right around freezing temps. HOWEVER, by the second or third season my worn studs were not as good as new Blizzaks. Once the studs get rounded they don't cut into the ice like new ones do.
Living on the east side, studs all the way and change them out after the second year. If I lived on the west side I'd run Blizzaks or Michelin studless on at least one rig, and put studs on anything I'd travel in.