It's funny you bring this up. I have a client that likes to do weekly calls. There was one I was on for an hour with one of his colleagues. I politly asked if he normally charges his consulting clients. He said no because he didn't like to get caught up in the small details but he said it's totally up to you.

I decided against billing because this man is full of knowledge and he teaches me on every call. So to me knowledge is priceless but not billable