I spent $150 on a fancy laser level for my basement framing and it completely burned me when the batteries died after 20 minutes. | DIY Disaster Tales - Rigidtalk
My buddy had the same thing happen with his laser. He ended up getting a cheap, old-school bubble level on a long board and just used a chalk line for the long runs.
Burning through batteries is just part of the game with tools. A corded level would be a huge hassle, dragging a cord around a dusty basement. That laser probably has a high-output mode that drains power fast, which is why it's so accurate. Maybe check the manual for a lower power setting to make the batteries last longer.