From the Car Talk guys about holding the clutch in while stopped:
"Dear Tom and Ray:
A friend of mine at work and I have a disagreement regarding using the clutch on a standard-shift car. He says that keeping the clutch pressed in will wear out the throw-out bearing, and I say it won't. For example, he says that when on a hill, the smart driver will put the car in neutral and let the clutch out, keeping one foot on the brake, to save wear and tear on the throw-out bearing. I say keeping the clutch depressed won't cause wear and tear. Who's right? -- Red
RAY: He is.
...
TOM: The second most common type of clutch failure is when the throw-out bearing (also called the release bearing) fails. That's the bearing that pushes the clutch plates apart when you push in the clutch pedal to change gears.
RAY: Used correctly, the throw-out bearing will last much longer than the clutch disc. But if you sit at red lights with your foot on the clutch pedal all the time, you can wear out the throw-out bearing before you wear out your clutch disc. And because that's an entirely preventable condition, we call that clutch murder in the second degree.
TOM: The problem is, if either the disc OR the bearing fails, you then have to replace the whole clutch. To reach either of those parts, you have to remove the entire transmission. And once you've paid for all that labor, you'd be crazy to do half the clutch. On most cars these days, a clutch job is at least a thousand bucks.
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Car Talk