BMW put it there. It is their policy for that transmision and model year

It means transmission lifetime not your lifetime. BMW don't believe that changing the fluid will extend the life of that transmission

I didn't, and still wouldn't change my x5 transmission fluid

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue