How often the water gets changed depends on the person manager
The store I usually visit changes out the water 1-2x per week.
Totally depends on the schedule of the employees and when they receive the shipment of the new fish.
The person in charge of the fish department will decide on the schedule. If no one complains they will do less WC's.
The employees the PS closest to me are usually pretty knowledgeable in the basics of f-keeping. Not so much when it comes to the plants.