Review (5/5): These last forever!
I just buy the cheapest Oral B rechargeable toothbrush. The first one I had lasted about 8 years and so I bought a second one. I don't have any gum or mouth issues. I'm not sure why anyone would buy a $100 toothbrush when a $20 works just fine. The secret? BRUSH YOUR TEETH! I floss at night before going to sleep. I brush twice a day. Because this brush has a timer, I brush for a full two minutes (don't leave the water running while you brush!). I feel like a powered toothbrush does a more thorough job than a regular toothbrush. I don't leave it charging all the time. It shortens the life of the battery. I put it on the charger when it gets slow.
I think this unit has been replaced with the flossing action version. Get one or the other and brush often!