Question about TP-Link M7650

What about the battery life of the *M7650*? Is the claimed "up to 15 hours" really true (or at least close to it)? The reason for my question: I have an M7450 and it always drives me up the wall because it often drains the battery within ONE hour (even when "doing nothing", i.e. without a connected device). This means that the device is always empty when you need it... :-(