Can't remember the last time - mostly because their wealth is enough to bail them out usually. I think if Arsenal are still atrocious by two-thirds of the way through the season they'll ditch him and bring in a rescuer.
I keep expecting them to turn it around and find form, or at least pull out some results, but it's not happened yet, I imagine that's wholly correct though and at worst they'll finish mid-table, probably a bit higher once it all straightens out