The manual (for my 08) calls for plugs at 37k miles at the latest, but BMW says this is a condition based service (CBS) so the computer will determine when they are needed. Mine got changed at 28k miles.
08 E90 | Jet Black / Black | 6MT
Mods: RAC RG63 w/ Pirelli Corsa 255F/285R | Akrapovic Evo Exhaust | OEM Blacklines
Winter Setup: OEM 18s w/ Nokian Hakkapeliita R 245/40-18