I have those tires on my (broken) mtb, awesome tires btw.

My brother is a frugal courier, and he bought some Bontrager kevlar belted tires for $80. He rode them until the rubber was peeling off in chunks, and I had to give him a pair of mine because he got so many flats.

You can keep riding on them until the rubber starts peeling off and you start getting flats from it. slick tires with treads are more of a marketing/image thing, the treads don't do much.