Seldom.

Critics may have minds of their own, but what chance have they to use them when experience in creating the art they write about is rarely theirs? So whatever they may happen to learn, and you learn from them, is very likely to put over on both of you as it was put over on them. Truth is seldom in the critic; and either good or bad, what comes from him is seldom his. Current criticism is something to take always on suspicion, if taken at all.

Frank Lloyd Wright, from A Testament

I don't agree with this, but it's interesting to think about.