Okay, I've done some "tests" with the controller. Damn, it's finally done; it took about a month to do.
The test was done twice, with one 4-hour play session per day with the controller not being used in-between. On the weekends, the controllers got much more playtime, but it varied a little (4-12 hours). Even with variations, all times were recorded so I could take the measurements. I played mainly Geometry Wars, Marble Blast Ultra, and let my mother play Bejeweled and Hexic, so there was little to no rumble used. The hour mark was an average between the two tests for each controller.
For normal play on the "non-defective" (no green light when off) controller with AA batteries, I got about 35 hours of play.
With rechargeable batteries on the same controller (doesn't have the light problem), I get about 28 hours.
With rechargeable batteries on the controller WITH the light problem, I get 15 hours of playtime.
**For the record, I own four wireless controllers. Two that I bought recently that are "fine" (no light problem), and two that have the problem. One of the controllers WITH the problem has quadrant 1 stay dimly lit, and the other has quadrant 2 stay dimly lit AND has quadrant 4 stay somewhat lit (brighter than Q2). I used the controller that only has Q1 stay lit, so the other one may be even worse. I may do another test on the second problem controller if people want me to*****