Probably never. In 2006~ BMW started making their cars less and less DIY friendly. The idea is that a person buying a brand new X5, 3 Series, 7 Series, or any other model will come back to the dealership to service it. They believe if you can afford the car brand new then you can afford their servicing. Its all about money. By the time people who DIY their cars can afford these their usually 10 years old or more. They want to mazimize the amount of money that they can generate per vehicle. The problem with this is eventually the people that do DIY their vehicles will want to buy them. But without being cheap to fix, or easy to fix people wont want them used. With no one buying them as used, the original owners wont be able to sell them in order to buy new ones. This in turn will eventually back fire on BMW, and all manufacturers that do this.
For example, in 1998 my 328i retailed for $37,000. 13 years later my car is now worth about $5,000.