Does it help to extend the life of the clutch and throw out bearing, if while stopped at a stop signal, to leave the car in Nutral, instead of with the clutch in?
Absolutely.
When you hold the clutch in you keep the throwout bearing under load needlessly. That causes it to wear out quicker.
The clutchplate itself won’t see any signoficant difference, but I’ll interpret your post as meaning “clutch assembly”, since replacing the throwout bearing is generally part and parcel of replacing the clutch assembly.
Yes, instead of lasting 300,000 miles it will only last 299,000 miles. This is like asking if I will get better mileage if I leave my lights off. Technically you will.
Really about the clutch question,most likely something else will fail long before the on or off the clutch issue becomes the condition that breaks the camels back.
In the days of really cra**y clutch systems (like the VW Bug and the dozens of ways the clutch can become inoperative) the question had more validity.
For most lights etc, it will be a wash maybe a little more or less wear. Now if you are talking about when you are stopped for a slow freight train then you want to put it in neutral and maybe turn the engine off.
Back in the 50's you would want to be sure to get it in neutral, but designs have changed in in the 60's they generally switched to ball bearings and the wear factor almost disappeared.Coming from someone who jsut had to replace their clutch at 160000 miles, it’s definitely a good idea to go with neutral, as when your clutch starts slipping, you’ve got 1 of 3 options- pay 1300 for a 200 dollar part and 1100 dollars in labor, replace it yourself, or ignore it until your vehicle is incapable of moving. Milk that clutch for all it’s worth.
The un-lubricated pilot bearing takes a beating also if you “ride the clutch” Use neutral…
Putting it in neutral or not will have no effect on the clutch, rather it will make a difference (little with modern bearings) with the throw out bearing. The “Clutch” only wears when you are releasing the clutch when it is in gear.