You definately can't be too stoned, I try to sneak a bowl in before I go in or on break.
I generally turn my brain off when im at work anyways, no one really knows the difference.
Bagging stoned is much easier, though I tend to put something off the the side and forget about it.
Usually I have to do carts once a week too, so I sneak a few bowls in the parking lot when I can.