I ran M60 on 2x18500 cells (Surefire 9P sized package bored to 18mm) non-stop and got a solid 2:17 hours runtime.
The cells were AW protected 18500 cells with 1500 mAh capacity, at 4.2V fully charged on Pila charger.
I think on 3x123 cells, which is what you are asking, you will get the same runtime.
Anecdotal evidence, but it seems that using the lite in short bursts results in lesser runtime. I don't have solid data to back it up and I am maybe 100% wrong here but that was my perception. If using the lite for 20-second bursts here and there, they just didn't seem to add up to 2:17 hours. Maybe there is a scientific explanation for this.
But that was one reason why I moved to M60L on 1x18650, I get greater runtime, enough practical brightness and the best thing is, I am able to use non-protected 18650 cells, which means it never dies on me in an insant.
Running M60 on AW's protected cells in some critical situation is IMO a very bad idea.
The module is (relatively) hungry, the runtime will go by faster than you think or perceive and will leave you in the dark at the worst possible time, just cut off with no warning. I don't know about other people but I cannot accurately gauge an hour or two, especially if it's not continuous but in small chunks and you are not really sure how much has passed and how much remains.
I was once fixing my radiator late at night on the side of the road, think 2AM and with 18-wheelers flying past me and of course the !)(*&# thing cut out on me as I needed it most. I got a reload going quickly but in the dark it's *not difficult* to panic and reverse the cells, frying the module, so then you have no lite at all (Unless you have a backup lite).
Use primaries (123) for anything remotely important... and enjoy 2 hours of regulated runtime and then a long tail of diminish lite. Protected cells are not the answer to everything and not for everyone. Come to think of it, I haven't been using protected cells in a long time now.
Or use 1x18650 cell, non-protected that will not cut out on you. You can see the thing get pretty dim below 3.7V so time to recharge. That's what I do.
If you want max power in small package, use M30. If you use a 3P body or a 6P with a spacer cell, you get very bright lite that won't cut out on you. I tested M30 on 1x123 and it seemed as bright as M60 on 2 cells. I didn't check runtime however. The runtime suffers but what do you care if you expect it, and carry spares.
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