My Sennheiser RS180 died a few month ago after about 8 years or so. They had normal rechargeable batteries, but it seems it was something else that broke down (

My Sennheiser RS180 died a few month ago after about 8 years or so. They had normal rechargeable batteries, but it seems it was something else that broke down (the batteries got replaced a few times). For my Sennheiser MB 660 I just replaced the ear cushions after about 3 years, but I am still 'worried' that some day the built-in battery will give up. Not because I can't afford new ones, but because I hate if a product dies due to an old battery. I own a few wired headphones/headsets, but there is none I used as much as my RS180 and when I think about it, I doubt that the cable would have survived the usage. Actually, I had to repair one of the wired headset once. The MB 660 can be used with a (removable) cable, but I use it only on airplanes or when the device I want to use has neither USB (dongle) nor Bluetooth. While I am privacy savvy person, my bigger concern is about health. Having an active unit all day in such proximity to my brain, makes me wonder if they are actually that safe to use.