How long do I boil store bought or canned tomato sauce for spaghetti? How long do I boil store bought or canned tomato sauce to use for spaghetti?

I know that tomato sauce can be cooked in cans that are available from the grocery store.  Why should it take 4-6 hours?
If the canned good is already "spaghetti sauce", it simply needs to be heated.  There is no need to cook it for hours.  If you are beginning with canned tomatoes, and making your own sauce, 20 to 30 minutes is usually enough to cook a basic Italian tomato sauce.