What is best practice for clearing the server caches?

PeopleSoft Supply Chain 9.2.35

PeopleTools 8.57

We have been running into some issues where sporadically users will get the not authorized when going to a page they have access to and have used previously. To resolve it sometimes if we have them navigate through Navigator or through our Custom homepages/tiles and then go use their favorite it works. This last time we had to clear app server cache as well.

We currently run the portal sync once a week. We have no set schedule for clearing cache on the servers, normally just clear app server cache if there are errors being thrown. Our web server cache hasn't been cleared for a year.