Maintenance schedules can't cover all eventualities of how vehicles were abused with short trips, etc.

If the plugs need replacing, then replace them. Mine are at 108,000 km and it runs fine, but I may do them next service simply because I won't still have the vehicle at 200,000 km, so I will need to buy one set (not two). I may as well replace them now and get the benefit from the new set of plugs as leave them to 150,000 km or so and change them only to sell the vehicle soon after.

The transfer case sets a code when it requires a fluid change. If you do it early, make sure you do the service tool reset required on the X3.

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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