Is this a standard firmware, no changes by you? One thing you could try is to check the file /tmp/browse.dat. There is a case where it gets accessed every few minutes or so. You can check this by doing an ls -l /tmp/browse.dat. What some of us have done to get around the issue of browse.dat being updated is issue the following command.
mount -o remount,noatime,nodiratime /dev/root /