I've always done it this way, do a session, check the pressures, make sure they are around 34 hot. Also depends on the tyre. My dunlops are fine at 34, a friend had yokohama R spec tyres and he needed to go a bit higher, was getting bad wear / feathering on the fronts. Increased the pressure and it was fine.
.: 2010 E71 X6M - stock, daily driver, towcar :.
.: 2008 E92 M3 - 6MT, Carbon Roof, Eibach Springs, Megan Axle Back exhaust :.
.: 1997 E36 323i Frankenstein - too much to list, track whore, stripped, caged, MoTeC, S85B50 :.
.: 1994 E36 M3 3.0 - 19" BBS LM Reps, Bilsteins :.