Hello,
Sorry, I meant to say that OLED display would be perfect if it draw same amount of power than conventional lcd, but it doesn't. Only good thing about it is that with it I wouldn't need to use any inefficient voltage regulation or converters.. Just directly use 3xAA batteries.
That LM295x looks very good. It seems to have low dropout voltage (40mV), so if I were to use 4 AA, it would work down to 1.26V / cell. Which is not awfully low, and it looks according to battery discharge tests half depleted battery.. If I understood right?