I have an older Dogtra 1200. The blinking low battery light blinks when it is basically dead. And I have to charge it every week. Are the new ones better/improved? The batteries have lasted about two years. I have been told the TT collars hold their charge for several weeks, can't over charge them, batteries last longer and when they begin blinking they still have enough charge to get through the day. What about the new Dogtras?