What is the best cost x benefit?




I´m new at the forum and pretty noob with leds (i´m working on it), but i made some iluminated furniture with them and it worked almost fine. Now i feel i should improve it.

For a cube of 16 I´m using 11 5mm leds (neutral white, 25000 mcd @ 30º) with 3 non rechargeable AA (4.5V). I´m not using any resistors. This configuration give´s me about 4 hours of good light, then it get´s pretty low. I need at least 7 hours of good light.

Now i think about using 3 Sony AA (2500 mAh 3.6V) or a PB 6V 4.5A to improve the duration, but what (and how many) led is the best for this (considering consumption and brightnesn)? 1W, 3W, 5mm?

Aready thanks.