Contact and Attention

How often should a mom call her daughters and how often should they contact their mother. Remember that if they contact their father, he may forget to mention it. My generation was used to a call once a week. My mother would not do long distance unless it was really important, so she wrote hr mother once a month. With cell phones, and social networking it is easy to drop a line anytime without disturbing anyone. But that is not enough! We want to hear our children's voices!! WE WANT TO TALK TO YOU. So, a phone call once a week would be nice in an ordinary circumstance. But, I found out that my husband tries to touch base with our daughters everyday to make sure they are okay in their distance environs. So, my daughters forget to call or return the call when I have left messages and emails. Why is this happening? It makes it sound like I am hovering, but i am just trying to get a response from just one of my communication equipment. I tried to make appointments to talk, I tried waiting patiently, and I have tried threats such as: " I am dying and need help". Nothing works. I have to go back to being patient. Eventually someone will need something from me and will call.