With completely wireless earbuds, the rule is: when the battery fails, they have to be disposed of. Not so with the Fairbuds, that allow you to replace batteries in just a few seconds. Combined with a repairable design, the earbuds should therefore have an extremely long lifetime.
If a device makes an encrypted connection to a server the device makers own, there’s nothing further you can gleam from studying the DNS lookups. They can route traffic through the first server, and they can resolve any IPs through the first server. And since you insist the person you’re replying to doesn’t know what DNS is because they said it’s encrypted, I feel you might also not know that DNS can be encrypted. In that case, the network owner can see that a device makes a connection to the nameserver, but they can’t see which addresses the nameserver was asked to resolve. And similarly, the device can refuse a connection to the wrong nameserver.