slicks

Can get hold of a new pair of Toyo RS1 slicks (GG compound) cheap and was wondering if anyone had ran slicks up front and R compound tyres at the rear? The rears will be Pirreli Trofeo R's which are pretty much a cut slick anyway, all 4 tyres are 205/50/15. I would purchase a full set of slicks...

Found myself what looks like a decent set of used Dunlop SP Sport slicks but it seems some race slicks don't have a manufacturing date. Guy said he purchased them 12 months ago from a Clio cup race team and they stated they has only completed 15 laps from new. So my question, what is the life...