Thank you all for your input and observations. I would not even know that the E70 thermostat might be a particularly troublesome part were it not for this forum. It's just something that I will pay attention to and keep an eye on going forward.

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8/2011 X5 xDrive35d Sport, Black Sapphire Metallic, Black Nevada Leather, Fine Burr Walnut Trim
2/2001 M5, Jet Black, Exclusive Complete Black Walk Nappa Point Heritage Leather, Black Cubic Trim