I've run snow tires in SCCA Rallycross, when I was too cheap to get proper tires.
On a moderately powered (~120hp) RWD car, the rear tires lasted about ten 60-second runs. Just plain wore out, turned to slicks.
On a moderately more powered (~180hp) car, I burned a set of Hakkapelittas out in eight. This was much more glorious, as this was on pea gravel and not clay, so I was ripping tread blocks out.
The kicker is, they aren't really all that much faster than anything else if the surface is tight.