How lone should AirPods last with full volume at 100 charge

Apple's guidance on your question:

https://support.apple.com/en-us/HT207012

Barry

It depends how often you have used them. When new ,at 50% volume, they should last 5 hr of listening & 2hr of calls.

Batteries in all electronic products degrade with time.

If you take calls on them a lot you should get a mix of 2-3 hrs

Ive had mine for probably around 10 months and get at least 4-5 hours when I watch videos online.. I don't use them much for phone calls though because people have a hard time hearing me on the other end without the background noise.