The Cold Shoulder?

How long do you let un-returned phone calls go before you start taking it personally? My long-time friend (18 years) is a very busy girl. I understand busy. When we have talked, she says that she was just getting ready to call me. My attempts to contact her are very infrequent, maybe 4 times a year. It's been around 10 months since our last phone visit, but I called her twice in September to wish her a Happy 30th. Those calls went un-answered. Does her contact info go into my 2005 planner?