The problem keeps returning
If you have treated an area and the activity comes back within weeks, the cause has not been addressed. That is the clearest signal to have the property assessed properly.
It affects food, guests or staff
Kitchens, food stores, guest rooms and staff areas carry consequences beyond inconvenience. Early assessment is far simpler than dealing with an established problem later.
You are about to buy, rent or renovate
A building about to change hands, undergo renovation or open for guests is the easiest moment to find and address pest conditions, before anything is closed up or covered over.