Too Much of a Good Thing?

Son #2 has been away at school for about a month and a half. I have missed him, but things have settled back into a normal (busy) routine, so I don't dwell on it anymore. Well, that, and the fact that through the miracle that is cellular phones, we talk or text nearly every day, sometimes a half dozen times. Lest you think I am a clingy mother, let me state for the record that it is HIM contacting ME! Truth is, he's taking 19 credit hours, but he's only in class from say, 10-2, so he has LOTS of free time even after his mounds of homework. His room mates spend their time partying and then sleeping it off, but my guy wants no part of that. While a lot of these folks are on the five year plan, he is posed to be done with at least one degree in two years or perhaps two in three years like big bro. Anyway, with all his free time, he reaches out to the only other person he knows who is almost always available - Mom. Now, don't get me wrong, I WANT him to feel free to call me. I feel bad that my oldest and I don't talk as much any more. But frankly, I run out of things to say to him and I feel like I am disappointing him if I have to hang up to deal with something going on with the other kids at home. No, I don't ever want him to stop calling, but I hope he will make some new friends and find some other outlets for his time.