Testing the life of different brands of AA batteries (test 1)

I use a lot of AA batteries in two of my cameras and the apparent frequency with which I find myself needing to replace them led me to this test.  Using my Olympus SP590UZ camera, I set it for time lapse taking pictures at 10 minute intervals and up to 99 exposures, which means a maximum of a little over 16 hours.  To test the batteries, I used three identical (except for color) single AA cell LED flashlights.  The batteries were

1.  Blue Flashlight (left)  Utilitech Alkaline battery (LG Sourcing, Wilkesboro, NC) (Expiration date January 2021)
2.  Purple Flashlight (right):  Rayovac Alkaline battery (Expiration date July 2024)
3.  Green Flashlight (middle)  Rapid Super Heavy Duty Battery (Ningbo Rapid battery Co. Ltd., (expiration date, July 2016)

10 minutes in they were all equally bright, apparently.

 After 270 minutes the Rapid "extra heavy duty" battery (middle) had started to dim noticeably (note the circle of light in the middle). 

  At 370 minutes the Utilitech brand Alkaline battery started to dim, and dimmed even faster than the Rapid Extra Heavy Duty battery.

The Rayovac Alkaline battery persisted until the morning light which somewhat spoiled the end of the experiment except that clearly by this stage it was clearly the winner in the battery life contest.  This was at 770 minutes.  

From this I have to conclude that the Rayovac batteries have roughly twice the life of the store-brand alkaline batteries (Utilitech) which in turn were only somewhat better than the "super heavy duty" batteries supplied with the flashlight.

I hasten to add that this was a single test using only one battery of each type and that to be statistically significant I would have to repeat this experiment several times with different batteries and for good measure switch the color of the flashlights around.  I might also consider doing the experiment in a totally darkened room so that the sunlight does not make evaluation of the flashlight beams 

I noticed too that once I had turned the flashlights off for several hours, all three of them had "recovered" their beam strength, at least for a while.  While the super heavy duty batteries began to dim within minutes the other two did not.  Maybe I should investigate this "recovery" and see how long the cells last after supposedly being drawn down almost to nothing. This last tendency is somewhat maddening when using a camera continually.  The batteries seem to be dying and then after a rest, they have a bit farther to go before depletion.