If you are worried about the filter, then change it. You can always put the old fluid back in.

There is no right answer to changing fluid. Nobody argues that it doesn't break down over time. The debate is whether it has broken down enough to compromise the transmission, compared to the risk of putting in new, high-detergent fluid. Your call.

I wouldn't change it. Again, your call.

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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