Never be afraid to ask us, we all have the same issues im sure. My husband wants oral as often as possible lol and I enjoy doing it. Actually I enjoy watching his reaction,that makes me laugh and gives me something to make fun of him about lol. But normal is whatever you two decide. If he wants it daily and that's too much for you then see if every other day works for you both. I don't know any man in this world that would turn down daily oral so you have to let him know what works for you as well.
My husband wants it daily and I will alternate sex with oral so he gets oral every other day unless I just don't feel like it then it'll be every two or three days. During my cycle if he wants it daily then that's fine, I don't mind then because usually i'll slack off the week after.
I'll do whatever I need to do to keep him happy but you do get tired of doing it daily, sometimes it takes the fun out of it. In this case I don't think there's a standard for oral, just whatever you two decide. Good luck with that. :)