Sony has always been pretty good in the battery life department, shouldn't it be possible to get more than 40 hours out of a single battery for a simple analog

Sony has always been pretty good in the battery life department, shouldn't it be possible to get more than 40 hours out of a single battery for a simple analog radio? Or is it rahter due to it being simple that they can't do better? Might be comparing apples with oranges here, but my PCM-M10 easily lasts >60 hours on two of such batteries. And that includes reading from SD card, processing/converting mp3, DA conversion and an LCD display.