I had 2 sets of Pirelli 225/60 18s, factory fit ones lasted about 21,000 miles, they were inflated to recommended 36 psi (bar is where you buy beer? :-)) Fronts rubbed off really badly on outside edges, so second set of Pirellis were set to 40 psi front , 38 psi rear, they were also rotated front to rear after 15k miles and lasted about 34,000 miles.
I now have 255/55 18s and run front at 40psi and rear at 38. Fitted at 55,000 miles, rotated at 70,000 and now on 91,000 and still a few mm of tread left, so may well be 40,000 plus on these by replacement time. Wear has been totally even on these.
2006 300C CRD
2003 AUDI A4 AVANT QUATTRO SPORT 3.0
1986 BMW 525i E28