I have studded tires (Kenda Klondike) that I use on an old mountain bike that I just use in winter. I sometimes wonder how necessary they are. In Minnesota, we don't have too much ice, just snow (it's commonly too cold for the thaw and freeze cycle). I'm thinking of running knobby tires this winter instead. The studs - particularly carbide studs on a fat tire - make for a heavy tire with lots of rolling resistance. Holding 14 MPH on the winterbike takes about the same effort as 20 MPH on a road bike (both on a dry road).

Carbide studs last longer than steel studs. The studs on my Klondikes have been through a full season and still more or less look new - I'd guess they'll last 4-5 seasons at least.