C..
I'm not sure this is a breastfeeding issue. I think this is a manners issue, and I would separate them and treat them as such. Certainly you have the right, the ability and the responsibility to claim your body as your own.... even though you are still providing nutrition for your son.
I would like to offer this..... you can't say that you are going to "nurse on demand" and then be unhappy when HE doesn't agree with your schedule, however. That's not fair to him.
Think of it this way..... giving in to EVERYTHING your son wants (by continuing to feed "on demand") isn't actually even healthy for him. It's teaching him that there are no limits and he will grow up to learn he will be indulged.
I think (I assume) that your intent for extended breastfeeding is to continue the bond you have with your son and let him know that you will meet his needs.
So.....
I think there can be a balance. You can still provide him with the nutrients and physicality of extended breastfeeding, but provide some structure that works for you.