My wife and I only do oral when we have enough time not to have to worry about how long it takes. I don't think I ever paid attention to how long she takes. I love
giving her head, so the longer the better. I like to give her as many little and big "earthquakes" as she wants. Usually I keep going for one more "O" after she asks me to stop!
I used to give head to a guy, many years ago. I do know I gave him head for almost 2 hours once. He was watching porn with me on my knees at his feet. After he came the first time, he told me to keep his penis in my mouth until it got hard again and then suck him off again--which I LOVED