2 - 3 trackdays, depends on a few things like Mike said.
Go easy on third when braking hard too. Mine went crunch when I stomped on the anchors with the car in third @ approx 7000rpm. Nothing but a death rattle when I put my foot down coming out of the bend - all the other gears were OK tho'.

Every time you hoon it you're going to be thinking "this could let go any mo'". No fun IMO so start saving for something stronger...

Newts