Use rechargeable batteries.

After two years of constant use in my headphones (8+ hours a day), I still get a full week's worth of power from each battery. I don't recall how long traditional batteries lasted, but I don't think it was all too much longer. I don't have any to compare it with as a major benefit is not needing to worry about buying batteries ever. I do need to make sure I keep charged and discharged batteries separate.