I've noticed the case with mine doesn't last particularly long. But it hasn't felt like an issue as the AirPods do seem to get excellent battery life and the case can charge them several times.
Today I purposely avoided using my AirPods just to see how the battery was when not in use. The case dropped 20% in 3 hours (AirPods were at 100% at the beginning of this 3 hour observation).
Actually what might be more interesting is to fully charge the case, and then when unplugging it also remove the AirPods. See if the case itself has some sort of abnormal discharge or if it's only occurring when the AirPods are in there.
It's a tricky product when you think about it, 3 little devices, each one with it's own battery and bluetooth connection, all in a tiny package.
Not surprisingly a great many people don't fully understand the relationship between the charging case and the AirPods themselves.
But that won't stop people from making threads about how theirs is "defective".
I think most people understand how it works, but what seems to be an issue (obviously not for everyone, or maybe not everyone is paying such close attention), is that some do experience a significant battery drain while the device isn't being used.
If someone has abnormal battery drain, is theirs not defective?
I don't understand why the case continues to keep the AirPods topped off when they're fully charged, hence the case drain in standby. You would think once the pods are fully charged they would just stay charged? Or is there a constant connection going on to where the case has to keep charging the pods?
This is no different than any other device. But instead of plugged in to the wall, they are in a battery powered case. Its to be expected.
I think what @ip67
meant was if the AirPods are fully charged, why are they not holding a charge state when they're not
being used (in the case).
I can absolutely and would expect some drain with time while they're just sitting in the case in standby and not being used. But one would expect that to be a very slow discharge when not in use, just like other electronic devices with lithium ion batteries.