I didn't finish reading all the posts, but thought this was a funny thread to see since last night on our way to a friends house for dinner I was texting my friend. Bruce says...why don't you just call her!?!?! I said because this way I don't have to answer if I'm busy or don't want to. We ended texting for about 15 minutes. LOL But I like the answer at your convenience aspect.
And sometimes one of us will text...you busy? And that means the other person wants to "talk" to you. It also came in handy before I moved in with Bruce. We'd text each other throughout the day while we were working. Well, that honeymoon's over.