The bigger/more relevant question is, where are the filings coming from? If you're stripping the wheel all the way down to the hub, spring for a "repair kit" and install new bearings. I just did this yesterday on my '92 500E, and the parts were less than $50 a side.
And if you bring the hubs into a shop to have them pressed in, it shouldn't take them more than 1/2 hr to do all the bearings
