I’m just running a few hypothetical numbers here. This is a xp-g3 test done by TA.
Given the 1AAA is making 40 lumens for 4 hrs.
That should be about 100ma at the led but because of the boost driver voltage conversion thats about 200ma from the battery, increasing as the voltage drops.
200ma for 1 hour is 200mah’s. So 4 hours needs about 800mah of capacity.
That seems about right when you factor in the losses in the driver from the boost conversion.
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Using 2 AAA’s you would still need a boost driver given the voltage will be below the vf during the discharge but not nearly as long.
So you wouldnt have as much battery energy lost during the run time because of the higher voltage to less current needed for the conversion.
But both running at 40 lumens the led has to be driven at the exact same current. So basically the only difference is you have doubled capacity with better efficiency.
So I’m just guessing with 2 AAA’s the light should run about 9 hours at 40 lumens.
Just my 2 cents 
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For 25 hours at 40 lumens, we know the led needs about 100ma. If the input voltage was dead on vf of the led and didn’t drop not even needing a driver.
1 hour at 100ma = 100mah
25 x 100mah = 2500mah
The 2AAA’s run in series has now become a single battery of 3v output with the same capacity as one AAA, about 900mah.