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.
You don’t think the Bluetooth codec makes a difference when you’re using Bluetooth headphones? When else would it make a difference?
I feel like you’re just confusing the codec used for compressing audio for storage and wireless transmission with the codec used for transmission via Bluetooth. That or you’ve just never experienced a setting where a better codec was being used.
SBC can sound okay, but see here for a breakdown of why it almost never actually does. Basically, it’s capped at only using a fraction of the available bandwidth, even though it could use more if not for arbitrarily imposed limitations.