Since your answer to question 1 is "never", this is an area of strength for you. It appears that you are not prone to quick negative judgments of new ideas as are most people.
During the fragile early stages of the creative process is not the time to test an idea's validity. Almost all new ideas have flaws. When you're too quick to judge, you often overlook what's worthwhile and drag down the entire creative process. Even if an idea isn't perfect, it's more constructive to look at what's good about it and keep making it better, rather than take the easy way out and drag it down.