Good cleaning, low life expectancy

Have me on 20/11/2011 the two toothbrushes bought. At 2 times will daily use one of the two handpieces until 24/12/2014 works perfectly. After that, the battery life of an average of 5 days reduced to 1 day and at 12.28.2014 presented the battery then his service be final one, regardless of what I was trying to charge the battery charger.
The cause of the failure, I suspect the battery as such as a charging current was measured.

With a useful life of 3 minutes per cleaning my bleeding gums is gone after 3 months, but 5 star and a thank you.
In a spare parts price of about 90, - Euro per handset and a shelf life of approximately 3 years my 30, appear - Euro / year is quite high, for 1 star.
Average: So 3 stars.

I'm curious how long the second brush my wife by holding.

From several previous recessions I could exquisite less operating time, maybe the problem is with the manufacturer and possibly at Amazon known therefore perhaps no warranty extension, as with other products will be offered common, a point which is taken into account in my next buying decision.

Addendum.
Having broken down the brush and removed the battery, I realized not the battery but the electronics of the brush is the cause of the loss of function. The battery is in good condition and has a decent capacity. The internal power consumption of the brush is in the off state so high that the energy via the charging circuit can no longer be transmitted ie the battery is not charged but discharged when switched off the brush.
Schade to replace the battery pack is the smallest exercise would have been, the brush can be split easily and a Lion Battery is getting for 6.-.

I am now in the process to remove the battery and to power the brush via a power pack with cable channels.