Average is three months. I ordered an X5 in July and got it in September. My '07 M3 was ordered at the end of August and took delivery in November. It's safe to say three months unless you change your mind and change the specs. Also a 10% deposit when placing an order, and another 10% when the production is confirmed.
E92 M3 2007 - ///PE with Test Pipes and BPM Stage II; CF Interior & Splitters; CIC with Connected Drive