Airpods battery life

Question

I just got my Airpods gen 2 a couple of weeks ago. However the battery life is nowhere near the 24 hours Apple says.

I took notes, and got 9½ hours of listen time, before the Charging Case was empty (5%; no longer charging the Airpods). Once the Case is empty, the Airpods slowly discharge, inside the Case, at around 6% per hour. This appears to be the case for others, but this would mean they would be empty within a day.

I exclusively use them when walking the dog, so 4 times a day, for about 30 minutes. I get only 4 days of use out of them, before I have to recharge them.

My question is; Is it normal to get so few hours out of them, with my usage pattern? Or should I have them checked out, by the store, under warranty? I know the 24 hour they promise is under ideal conditions, but getting around half that seems odd. Other than this, I'm really liking my Airpods.

Some additional info:

1. My volume is always below 50%
2. I have them connected to my iPhone 8 (which supports Bluetooth 5 AFIK)
3. "hey siri" is disabled
4. I only listen to podcasts (Overcast App)
5. After walking for half an hour, the Airpods charge is around 90-93%, which is about right (10% of 5 hours = half an hour). When I put them in their case, and wait for them to charge up again, the case looses 6-8%. One would expect this to be only 2-3%.
6. I measured charging only the case with a generic Charger Doctor, and got 326mAh of current usage (5% -> 100%).
7. One would expect the case to add 19 hours of usage (i.e. 24h total - 5h for the Airpods themselves). So I get exactly halve.
8. I tried looking this up, but everyone is only talking about the battery like of the airpods themselves (5h), not the case (or both combined).
9. (I don't live near a Apple store)

Answer 1

Apple:

A single charge provides up to 4.5 hours of listening time or up to 3.5 hours of talk time on your AirPods Pro. If you charge AirPods Pro for 5 minutes in the charging case, you will get about 1 hour of listening time or about 1 hour of talk time.

As mentioned in the comments:

No, it's not normal battery life. You should just return and replace them

Note: Telephoning, for example, puts a particularly heavy load on the battery, but even listening to music usually brings the editorial staff's Airpods to their knees after just under an hour and a half.