If there is a specific issue that you're experiencing with your system that a BIOS update may/will fix, then this mandates the need for updating. If you're just looking to update your BIOS for the sake of having the latest BIOS, I would not try to fix something that isn't broken!
On my PERSONAL systems, I update no matter what whenever a new BIOS is available. For clients, if they aren't squawking, I'm not talking!
In order to update correctly, you MUST know who made your mainboard, the model and quite possibly the revision. Flashing with an incorrect BIOS will make you sad.
-DAK-