The problem you face is that a small number of people (statistically) have had them fail, but the consequences of failure can be expensive as these engines do not tolerate overheating very well.

If you do decide to replace them, recommend you replace all hoses with coolant in them, as well at the thermostat. Think about the water pump as well. I would probably do the hoses and thermostat, but not the pump. If you do replace the pump, use OE and check out the warranty term for it.

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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