And it appears to have been introduced in 2014 so be sure you are not dealing with a few year old device.
As to the battery, this looks to be the usual sealed device that is not made to be serviced.
That said, the replacement battery would give the same time as when it was new (give or take a few percent.) So when these start to fade you start shopping.
PS. I moved back to a wired solution as it's one less thing to charge up.
I am trying to find out if there is a battery in my device that can be replaced to improve the usage time. I've looked at the user's manual and it doesn't say.