The plastic halves of the earbud casings are ultrasonically sealed together; you have to break them apart to get at the guts (and IIRC the battery is also soldered in). Just look up the iFixit teardown; they're completely unrepairable.

Their lifespan is, at best, the lifespan of the battery (in terms of useful recharge cycles). This is the dirty secret of the vast majority of wireless earbuds on the market, regardless of their cost.