Blimey that's more frequent than me!  Though I'm only cleaning around 30 houses a week, trad only.  I flip the rubber every 2-3 weeks, but find the flip side only lasts 1-2 weeks.  It's always the corners that go first with me, so I'll change it then, or if it lasts 3 weeks then it gets changed that weekend regardless.  Nothing like wasting a bit of work time changing the rubber to p*** me off!