If it was Boeing's shelf, then who replaced the batteries? If Boeing took possession of the units and shelved them, then they'd be responsible for maintenance. Seeing how this was not standard in-service fleet maintenance, who did they send into the warehouse, screwdriver in hand, to swap the batteries?
Great point. Say if the ELT were manufactured in 2006, someone might find it prudent to put fresh Lithium batteries in them, since they are supposed to be good for 10 years, before installing them in a plane finished in 2011 or so, so the carrier wouldn't need to turn around in 2016 and replace the battery. Someone unfamilier with the particular ELT, changing the battery, would explain a lot. Honeywell should put a tamper evident seal on there various beacons, and require that, when their battery is 10 years old, the whole unit be swapped with a new one, and the old one sent back, to get a new battery. One of those "No User Serviceable Parts Inside" kind of things. It's for what is sometimes referred to as "Post consumer control of your product". Maybe it's already like that? Maybe someone on the forum knows?