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.
I bought the 4 from Mureno with e/os/ on it.
I’m curious what made you not like e/os/. I’m interested to try it if they do the fairphone 5
I didn’t have strong feelings about it, and had extensive experience with LineageOS. I just stuck with what I knew.