What’s a normal amount of time to get hard for round 2 as a 24 year old?

I (24) am a sexually active male who has sex with my girlfriend multiple days a week, usually going 2-3 rounds each time. I never have any issues getting hard for round 1, and we are both left very satisfied.

However, I find it sometimes takes 30-45 ish minutes to get going for round 2. My girlfriend is usually expecting me to be ready again after like 10 minutes and I feel bad when that isn’t the case. I just wanted to know if that’s a normal thing or should I be concerned that I’m not ready sooner?