Hi
Are any of the buttons not working on your remotes. Just wondering if you have a switch permanently on. But not sure if that would cause batteries to fail early but worth a check. I had a switch in the remote fail but the battery was ok.
But had to replace a switch, the "unlock"one had failed.
Each switch normally makes an audible click
http://www.volvoforums.org.uk/showthread.php?t=201489
Iain