That is a nice opinion question. They pay me my monthly income, so my work does have some kind of "value". I always stay minimum an hour longer than necessary, but very often I find that there is not a lot of recognition to that extra work beeing done.
Since I am responsible for the whole production during my shift they are kind of "forced" to value it. Two days ago I told them I'll quit next month cause I hate that place, the shouting reaction with the words "you can't leave us alone here" was the only time I got the feeling they "need" me.