Nothing has changed much about how battery life may be tested or reported. Here's some of my thoughts on this.
1. The battery life as reported is now pretty much true when the battery is new and under "their" selected conditions.
In about 18 months, you may find that most batteries have less than usable time, so take that into account when figuring out how much it costs to maintain such an unit.
2. The reviewers rarely get the luxury of spending more than one or two attempts at seeing how many hours the battery will last. The backlight item, while interesting to some may have neglible effect in most cases since the common use would be to turn it on to set the device up and playing, then it would go back off. Effect may be a 1 or 2 % hit on playtime. Moving the volume up could have a far greater effect.
I was looking at the reviews for the Gmini 120 and 220. The manufacturer says that they both have a 10 hour battery life (which I doubt, seeing as how they are the manufacturer), but Cnet says the 120 has a 9.5 hour battery life, while the 220 has a 6.5.
I looked on the MP3 player testing page, and saw how battery life was tested, but, I'm curious as to what the settings for backlighting and contrast are durring battery life testing. The 220 has a larger screen, so backlighting it, especialy with high contrast, would be more draining than it would be on the 120. Does anyone know how Cnet does backlighting and/or contrast settings while testing MP3 player battery life?