-My SQF auditor was MOST concerned that the traps were at either side of any door or possible entry point for pests. And all they really want to see is a floor plan proving frequent preventative controls. I don't know what your facility is like, but I can tell you my auditor did not care, as long as there weren't any signs of pest activity anywhere.
-If you take a pest control course online, they offer guidelines on equipment, like how often it should be placed. Go to the manufacturer of your trap for their advice.
-I also think frequency is variable based on the facility type and location. What are the risks in your area? SQF NEVER gives clear black and white answers.
My best advice is to have them properly set up on either side of any entrance. That's the biggie.
-And may I just say, you can ABSOLUTELY create and operate your own program. If you get certified or take excellent training, depending on your facility needs one could argue that it's BETTER to have your own program. You can monitor much more frequently than an outside contractor can. And your team can respond to emergencies better. I had a contractor take THREE days to respond to my request to visit.
No auditor or consultant I've spoken to has said it had to be an outside contractor. Some facilities are very easy to control pests, some are not. So it definitely depends on that too. If you have limited risk, a well secured location, and want to use only all natural , nontoxic baits, then there's no reason not to train someone on the team to manage a pest program.