By not servicing transmission youre rolling the dice. New fluid will always be better than old fluid.

Brake systems are hydraulic and for all intensive purposes sealed. They need service. A transmission is a mechanic component. Why would bmw put magnets in the trans pan if there was no worry of metal particals contaminating the fluid? Those metal particals need to be removed periodocally as they can clog passages or cause even more rapid wear on othe components.

Its your own choice ultimately, but it is a gamble that can more than likely have the odds swung in your favor with preventative maintenance.

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Current Bimmer
2004 X5 4.4i Sterling Grey Sport/Premium

Past Bimmers
1991 318I Alpine White
1995 740I Alpine White
1991 525I Schwartz
1998 323IS Scwartz
2004 330CI Cabrio Titanium Silver Metallic
1995 540I Schwartz
2000 Z4 3.0 Titanium Silver
2000 330ci Coupe Titanium Silver