It's just that those are the things that get the most heat and the most gunk on them. As far as I'm concerned, they're sacrificial.
Ken upon a recommendation I placed a sheet of expended metal over the top of the flavorizer bars on our Genesis and then placed a layer of lava rock over that ... works like a charm and it seems to add a little flavor to the food grilled.
To the original question, I'll do a thorough washing of our stainless Weber grill every few months with Dawn dishwashing liquid, let it dry and throw the cover back on. Keeping the cover on and staying away from the abrasive or acidic cleansors is key with a stainless grill in my estimation.
