This is totally acceptable. If it isn't acceptable to him (and if it were me in this situation, which I realize it's not, but still...) I would have to think twice about being with him. Your phone isn't always going to be attached to you. For example, I don't text while I'm at work or in class, or of course, driving so it may be a few hours before I get back to someone. And what if you fell asleep at 7:30? Haha, I've been so tired from my nursing clinicals that I've done it! Anyway, that's just my opinion.