I should not tell everyone this, but I go in and change the battery every 6 weeks, my Father and Grand Father also changed the battery but it was every 3 to 4 weeks,<br>batterys have improved since their days!,(reply>), @frzstat Great minds think alike :),(reply>), I thought it was like a smoke detector, you changed the battery every 6 months, but on night shift when all the scientists have gone home :)