Not that I know of. I've never even seen a self-checkout at Lowe's. I know that they should always have at least one cashier or somebody up at the return desk.
Not really a cut off. Staffing is scheduled by trends. It's computer generated. Stores have very very very little control over it. Plus self check can not be left unattended. Usually in most stores you'll have at least one lane open and self checkout open. They do have to split off for dinner break. Customer service should be open at all times as well. It's usually for order pickups and returns but will usually call people over if line gets backed up.
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