I bought my Sonicare in about 2000 for about $80, didn't start using
it until 2003 and it is still going strong. I use it once a day and
miss a day sometimes. I usually run it for the pre-programmed 2
minutes plus another quarter or half-cycle, so about 3 min per day.
As
Meat Plow reported, I see no indication that the charge capacity has
been reduced.

Normally I put it right back in the charger after I use it but I have
left it out of the charger for up to a week before I had to recharge.
The charger is in another room so sometimes that is more convenient.


I don't know how all the other electric tooth brushes work, but the
Sonicare uses a magnetic signal generated by the handle/battery pack
to make the brush oscillate very fast. I don't know the actual speed
but I would estimate 50 - 100 cycles per second. You would be
brushing
for an hour to get the same number of strokes by hand and I can't
believe Consumer Reports still preferred a manual brush. The Sonicare
does an amazing job of cleaning my teeth and I knew the first time I
used it that I should have started using it sooner. My teeth felt
totally smooth like after the dentist cleans them.


I have never submersed the battery pack in water because it doesn't
look waterproof, but it is at least water resistant because I clean
the cavity where the magnets go thoroughly a few times a year using
water and have never had any problems doing so.