As long as there is something in the device limiting current, the available battery current makes no difference. If you had Hoover Dam attached to your laser, as long as that dam's output was DC and regulated to your target voltage, you'd be ok (and powered up for life).
In an incandescent light, the current is regulated by its resistance (and a relatively stable input voltage); in a laser or a led, the current is usually regulated by the circuitry (although some led's may get away with no regulation as long as they are carefully matched to their power supply).
So go ahead, pile on the batteries! just keep 'em side by side, parallel-parked so to speak.
In an incandescent light, the current is regulated by its resistance (and a relatively stable input voltage); in a laser or a led, the current is usually regulated by the circuitry (although some led's may get away with no regulation as long as they are carefully matched to their power supply).
So go ahead, pile on the batteries! just keep 'em side by side, parallel-parked so to speak.