I am glad that you are 'acting as if' it doesn't bother you. I think it is ok when he calls to say kindly...'hey, thanks for calling, but I wish I heard from you last night'... and that's it.
I think it is great that you are having a great time together. I think that you bring up a good point. I don't think that having a good time together gives him the right of way or let's him take you for granted. I feel that by not blowing up in anger and blaming him is a good thing. I think it is great that you let him deal with his mistakes and his bad choices by himself. Don't spend your energy (at least in front of him) fighting about it. If you do, he will probably end up turning it around and point his finger at you. Then he will rationalize that he has a reason (although a false one) to do it.
But, yah, next time when he does it and calls just tell him... 'Nope, that wasn't ok, but thanks for asking.'... then continue with whatever you were doing.
It's awesome that you guys can have a good time together. I am hoping for 'the day' when my 'H' feels comfortable enough emotionally to be with me again. After 1-1/2 years of not talking to me after 'he' left, he is now able to call me once every three weeks (maybe). He took me out for my birthday, July 31, and I haven't seen him socially since then. It is difficult for me to remember to be grateful for the little bitty movement on his part are positive steps.
I have an appointment tomorrow with a DB coach. I love her. She helps me align my emotions with my goals.