I am using Philips QT4011 for more than a year and even from the very first day I find its battery backup is very bad. It can't stand even for 15 minutes. As written under its specifications its battery can stand for upto an hour after a full charge. But I seriously never get that much of battery life in this trimmer.
Except battery life all other features are perfect. It runs very smooth, nice grip in hand, a curve in its design makes it easy to shave on the neck region. But if its battery doesn't perform well then all other features becomes useless.