The batteries last one year, or two as much, after which time you will have to recharge the brush with every 2-4 minutes of use. So do not buy the more cool LED display model, etc; just go for a basic model, as all of they are mere DC motors with basic mechanism, with basic batteries.
The bristles of the brushes, are designed for deliberately to lose stiffness after X time (or at least it is what happens with Oral-B, two months in my case), what in my village is called programed obsolescence.
The inconvenient related is I can not disinfect so often as I was used with effective liquids the brush before use it, as it hardly accelerate the programed obsolescence of the brush ( By degrading quicker the colored "paint" what maintains the bristles rigid and usable). I wonder if they degrade equally with UV...
So I am always trying to find more resistant or durable bristles compatible with my machine, hacks, brands, etc, because after using an electric toothbrush usually one don't look back, what is my case.
One day I decided to give it a try. A few months later, for my next visit, he didn't bring it up.
My conclusion was that he could genuinely tell, when cleaning my teeth that I had been using one. Therefore they must really be better at cleaning. I stuck to it and can't complain.