Flashing the BIOS should only be done if you are having a problem with your PC. Generally, by that, I'm talking about hardware recognition or something that is causing a problem booting. It is not something to be done on a schedule, and while flashing a BIOS is simple enough, it is also somewhat risky if anything goes wrong during the flash. Chances are that if you aren't having a problem with booting to XP, you won't have a problem with W7. Bottom line is don't fix it if it isn't broken.
Rather than flashing, I prefer to buy a new chip. It is super easy to install, if your MB's chip is socketed.