I have two of these devices, purchased in late 2020 and early 2021. The first soon stopped working, it was replaced under warranty. Both have experienced problems over time. Firstly, the promised 10 hours no longer applies, it is now more like 6 hours. Secondly, both devices did not stop charging, but discharged themselves in the process (the charging light did not switch off), so that they went out, barely used.
Two measures have helped so far. First, when I put them in the box, I make sure that the handsets are actually resting on the charging pins. Secondly, it has proved helpful to switch the unit off completely after use by pressing the right handset for five seconds (sometimes more than 5 seconds, just until a tone sounds). In any case, the claim that the earpieces switch off when placed in the box does not seem to be true (any more). In the meantime, the headphones work reasonably well, but I would not buy the product again.