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.
Just to be pedantic; a battery is significantly larger than 2 tiny wires of copper. The battery is almost 50% of the volume in the earbud.