With my knowledge of hardware design I'd say that:
- when the mouse is on, either it just stays still or not, or you click it or not, it conserves around ~1mA (average of active and idle modes);
- when you move the mouse, if the mouse is optical, the led at the bottom side of the mouse is lit, and it conserves additional ~10mA for low-power leds and ~20mA for typical ones (let's take average 15mA);
- when you don't use the mouse at all, it's tiny microcontroller will sleep and wait for interrupts (buttons / optical sensor), which basically will also will drain battery, but very minimal (like ~0.07mA - tinyAVR sleep power);
- and sure, if you push the off button on the bottom side of the mouse, it will be completely turned off (you will need to press the same button again to make it work - my wireless logitech mouse has this button, others may not)
Considering you're working with that mouse 10 hours a day, and you move it half of that time, and your mouse is sleeping for rest 14 hours of day, you get:
Iday = 10*1mA + 5*15mA + 14*0.07mA = ~86mA per day
Ihour = Iday / 24 = 86mA / 24 = ~3.6mA per hour
Let's say, you use 2 AAA Alkaline batteries (each is 1200mAh) = 2400 mAh
There is a lot of online battery life calculators, where you can put those numbers.
According to this calculator, mouse battery life (under mentioned conditions) is:
466.667 hours = 24.4 days [average battery life for active user]
- Buy chargeable mouse or get nuts in a three months!
- Try to move mouse pointer with your finger, but click/scroll with the mouse. This will increase your battery life a lot.
- In an ideal world manufacturers will not use any leds in their mouses at all, they will think about consumers and environment. But this will never happen in ours.