The branch in North Carolina I visited has an Audiologist manager and a couple of HIS / trainees. The Virginia branch I visited was relatively new. They only had one person. I am not sure if he was an audiologist or HIS.
The people here have years of experience. The manager is HIS with 12 years at this Costco. The HIS who fits me has 7 years here, and 15 years running his own clinics in other states. Two other HIS here have 9 and 7 years. Only one person is new and she just received and Ph.D. recently (not sure in what discipline) and still needs to get certified, so she is support only for now as I understand. This Costco is open Mon thru Sat, and plans to add Sunday hours soon.
Part of this longevity is the fact that San Luis Obispo (central coastal California) is a beautiful and very desirable place to live, so those with good jobs have little reason to leave the area.