Do you think its better to have a published date AND a last updated date on Posts ? Does google even look if you updated but left the published date old

I was thinking of adding a "last updated" field to my articles. But is it worth it? or should I just keep it uncluttered and leave only the last published date? I would think that Google would not notice if I updated a last updated meta field since their is a published date field already.

Thank you for your response.

If I am going to NOT include a date on some posts - How would I go about doing this?

I use wordpress, and the post date is included in the post meta field by default when a post is published. I do not think that simply using css to hide the post date by "display:none" is the correct way, since that would only hide it from people and not from a google crawler. And I would NOT want to hide the date on ALL posts - Only on some posts. Do you know how I would go about implementing this? Would this require that I make another post template or something?