The batteries will degrade with time. And besides don’t you want the newest and best when you replace the next one.

You might look into getting one that warns you audibly of pushing too hard, you just want to run the brush over your teeth, my cheeks and lips apply enough force. Talk to your dentist, they know best.

Unfortunately buttons don’t last forever, although newer buttons may survive more click cycles. I’m would be inclined to believe my Philips Sonicare will outlast me. (top model at the time, but I don’t like the new brush head tracking system, seems more expensive than it’s worth.) Just change with the seasons. I’m going to start doing mine on the equinoxes.