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.
Buds can be used without an app, but they really should open source it if they really care about long term sustainability.
Imo its fine if they open source it when they decide to end support. The fact that app has a pristine privacy record is good enough
They should also have a wired option. But I guess that they removed the headphone jack from their latest phone for a reason.