Not too odd. Up to 5 hours on listening and up to 2 hours talk time. I do get approx. 1:45 on FaceTime Audio calls.
15 minute charge gives you another hour talk time.
I had been on a longer road trip and was on the phone for over 3 hours. Just plug in the other left AirPod at the low battery warning. The call will be on both. Take the right one out and put into the charging case. This is seamless and the party on the other end didn't notice anything.
This will allow approx. 15 hours of continuous talk time with a fully charged case! That's better than any of the many dedicated Bluetooth headset for phone calls I ever owned (Plantronics, Bose ...). At the same time the call quality is better too.
This was a voice call actually, so it was particularly odd