Rob, you'll DEFINITELY know when your valley pan quits on you. It usually works something like this:

You have a "low coolant level" message on your dashboard. You go out in the morning and top it off with your 50/50 BMW-branded antifreeze (being sure to use the bleeder valve in the proper manner of course). In a few days the same thing happens again. Then, at ever-shorter intervals of time over the period of the next week or two, you find yourself repeating the same process above. You look and look but you just CANNOT find where the antifreeze could be leaking from because you don't see any obvious indicators in the engine compartment.

Then - one morning you awake, and you notice what must be QUARTS and QUARTS of antifreeze on the ground underneath your car. "Crap..." you tell yourself, because you realize that your valley pan has just completely failed on you and you now have about a $2500 - $3000 fix on your hands.

All because of a crappy $90 gasket that wasn't properly manufactured by one of the Mexican (er...bmw "authorized") parts manufacturers (that's right kids, we pay GERMAN prices for parts made in fu*king MEXICO)! And instead of BMW doing the right thing and paying for what was an obvious manufacturing flaw, they stick YOU the consumer with all of the parts and labor costs to fix it years later. You can comfort yourself though with the fact that, even though BMW denies any and all knowledge of the faulty OEM gasket originally installed in your vehicle, they have nonetheless taken great pains to COMPLETELY REDESIGN a gasket that does not need to be redesigned to avoid any future problems we might potentially encounter. How thoughtful and clever...preemptively re-engineering parts in advance of any problems that might occur. Now THATS why you buy a BMW...

...NOT!!!

All ranting aside, when my valley pan gasket went out I took advantage of the situation and literally dropped the car off with a box of pre-purchased cooling system replacement parts. Since the dealer had to take them OFF the car anyway to get to the valley pan, they had put them ON for free as part of the valley pan gasket replacement process. The parts I got replaced for $0.00 in labor costs included the water pump, thermostat, all belts and most of the hoses. I also had them check for dried and/or rotten hoses near the rear of the engine (many threads on this forum about that) and also had some of those replaced at the same time for a small parts charge.

I hope you don't have to go through this but it IS a BMW after all...good luck!