I would go off it the max wattage of the power supply the whole system uses instead of what the laser says.

That will have you covered for peak draw over the entire duration you're looking for, and will likely end up giving you a lot of wiggle room time wise.

I know almost nothing about laser engravers, but many of them are mechanically similar to 3D printers, which I do know a lot about, and stepper motors can suck down a lot of power.