Finish fast?

I’ve been seeing this guy. He’s the second person I’ve ever had sex with. It’s been quite awhile for me so I’ve forgotten what’s the average round etc. I feel like he’s usually finished within 15 minutes. We haven’t done much foreplay. His size satisfies me, although I haven’t actually finished myself yet. I don’t know if he finishes fast because the sex is really good or if he’s too high? Perhaps both? also notice when I’m giving him head he tells me to slow down because he’s close to finishing.