My mom and stepdad, once I went to college (which is when he became my stepdad), got an 800 number for their phone, so that I could call them and it was always on their dime. They would get annoyed if I used my long distance to call them. My mom and I talked ALL the time, it didn't matter which one did the calling.
Once I got a cellphone I didn't use the 800 number as much, b/c it wasn't as important (I was paying for the minutes anyway, might as well not have two people paying for the call), but we both still called.
After she died, stepdad kept the number but then when he got remarried and moved that number went away.
My dad has always been a piece of work when it comes to calling or not calling. He has always thought that "I was thinking about calling you for the last" x number of months or even years actually "counts". (what's scary is to watch myself go into that way of thinking!)
But in my family no one gets on anyone's case for not calling; if we haven't talked in awhile it means that NO ONE has called, so there are usually apologies on both sides!
On hubby's side, though, his mom wants a schedule "say hi and how are you" call. It so incredibly meaningless! We haven't spoken since January '07 (though I encourage DH and DS to have a relationship with her) for many reasons, but the kicker was after I spent 90 minutes on the phone with the IRS, finding out some Very Bad News about the state of her taxes thanks to her just-passed-away husband (problem with turbotax e-filing is that it only requires signatures from both spouses ONCE, so if you're in a bad relationship the tax-doer can lie and lie that taxes have indeed been filed for, oh, the last 6 years). I went through the wringer for her, after spending the last 2 months doing EVERYTHING paperwork-related after FIL's death. She didn't miss one month of pension or social security, she got everything taken care of for her, and the only thing she had to do was get on the phone, verify identity, and say it's OK to talk to me (she's Korean and not comfortable speaking English to strangers). I spent 2 months and then 90 minutes, and 2 minutes after I explained it all and what she would need to do....she said "can you do me a favor?" She wouldn't say what it was until I agreed. I said yes, and she said she just wanted me to call once a week, just to say hi...and I exploded. Her other son and her daughter had ignored her for those months, I did everything for her, everything REAL and meaningful, and she ruined it by wanting me to do something stupid, nonsensical, and for face-value only so she can tell her relatives in Seoul that her DIL calls her every week...
She has continued to try to get her kids on a schedule of calling, but she never calls, and the calls are NEVER for anything more than "I need this from you" or "how are you" without listening to the answer. Every so often Robert will call her to talk, and she has expressed astonishment that he does that, b/c her other two kids (who agreed to the schedules) just say "hi how are you bye".
I can't imagine planning on not calling my son when he grows up. Sure sometimes I might catch him at a bad time, but I hope he can either not answer or he can say "oh I'm doing xyz right now, let's talk later". I remember how warm and cozy it felt, even if I acted annoyed, that my mom was calling. And she was always calling just to talk, to find out how I was doing and what I was thinking about...she put a warm blanket and a hug around me from across the country, and I can't imagine leaving my son cold and alone, just b/c I didn't want to bother him while he was doing something.