I just noticed that someone said it should last for 100s of hours in sleep mode. I tried that link but it didn't work. I am 100% sure that I do not get 100s of hours on DS games when I close it, even with a full charge. I'm sure I've never even be able to go for two days (48 hours). Perhaps the article refered to a DS and not a DSL, although I thought the DSL had better battery life (when the screen brightness isn't all the way up). When the lid is closed, screen brightness should be irrelevant (since it turns the screen off). Maybe some games are less CPU (power) intensive in sleep mode; I tend to only do it on games where I can't save frequently.
Sorry for the bad link.
The faq I referrenced is for both the DS and DS Lite. Here is the relevant paragraph:QUOTEHow long does sleep mode last on a full charge? I tested out sleep mode
on a full charge to figure out how long it would last. After 120 hours
on sleep mode, I finally gave up seeing how long sleep mode would last.
Then I played Super Mario 64 DS with both backlights on and full sound
for another 5 hours before the battery died. That being said, the DS
probably lasts a good several hundred hours on sleep mode.