There are varying opinions on that. Don't listen to GM. If you baby it and treat it right, the SC will be the last thing left after your car falls apart. I don't just change mine. I flush it. And I do it once a year. It'* cheap and easy, and with the added stress the smaller pulley puts on it, I think it'* worth it. I think 30,000 miles would be minimum, and if you don't know when it was done last, do it soon.
There'* a thread here in forced induction on this topic. Read some other opinions on it. That SC is nearly bulletproof, but only if you take care of it.