Logitech M705 Wireless Mouse: Are the batteries dying, or does the device have a hardware failure?

I've had to have my M705 replaced by Logitech two times due to the issues you are describing. The mouse button switch wore out. (they don't make them like they used to) And I only had the first mouse for 9 months and the second for 5 months. Both were replaced before even the original batteries had ran out of power.

Note that I have an existing question: Logitech M705 left mouse button doesn't stay down when pressed

I recommend calling Logitech, going though their questioning, and getting them to send you a replacement.

To answer the original question, in case someone actually stumbles upon it:

The SetPoint software which can be downloaded from the downloads link in the question should provide information on the battery status and have an estimate of number of days the mouse can be used. In addition to that, once the batteries reach the critical stage, it should also provide pop-up which will inform the user that the batteries are almost dead. Do note that the meter is calibrated for alkaline batteries and may provide incorrect information with other chemistries. Manufacturer provides an illustrated use guide for the software here.

If the use of that software is for some reason not desirable, the LED on top of the mouse should provide information when the battery level is low. Unfortunately, the product page doesn't go into details on how exactly this is achieved, but usually the LED will have two colors. One for use when mouse is just turned on and to signal that mouse is working and another which is only used when battery is low.

I had this problem. I read another post on a different site suggesting the use of compressed air to clear the laser. So I blew hard on the laser, once, and it sorted the problem out immediately. If only all problems were this simple. Paul