Yes battery quality and true capacity is the most important factor...
However there are other things that will determine how long your run time will be between charges.
There are differences in efficiency for any build. Especially DPSS.
The quality and type of driver used will also affect how much current draw demand the battery will have.
As your battery drains, the voltage is dropping, if it is a quality driver that has good regulation to the pump diode, then there will often be more current demand on your battery as it drains and drops in voltage.
If the driver is not giving good regulation, then your diode output will be less as the battery drains.
Etc, etc...
You can test battery current draw with your DMM and see what current is being drawn at full charge with the laser on by touching one probe to the battery, and the other to the host bare metal.
It will probably be between 750mA's to maybe 1.5 Amps for that laser. (guessing)
If it were using exactly 1.5 Amps and stayed at that current draw, and you had a true 3000mAh's capacity, it would be about 2 hrs. run time between charges...
So you can get a good idea of a close estimate, but your true run time will have to be tested. Just check the voltage once in a while until you get a feel for how long it can go between charges...