Over here there are numerous reports of SMW studs wearing through to the inside. It happens to Suomityres/Nokian eventually too, but usually at a higher mileage.
You can eke out a little more life out of them by lining the tire with duct tape, if you want to put off buying new tires to next season.
And while your center studs certainly sees most action, I'd be wary about trading down. It's like removing the compression bandage from the first aid kit based on "it's only the band-aids getting used anyhow".