I have a QGIS project where I am connected to about 10 databases. The issue I have is that I cannot seem to save the password to disallow repetitive password authentification. After logging in individual databases and working on the project when I pan around a request comes to log in after a few seconds. I have seen somewhere it suggest that I save the password when I do the connection to the database, however in QGIS 3.6, this seems to be different or I cannot get it right, after storing credentials, and not working on the project for a few minutes, when you come back it will ask you for the password again. This link here suggest it is a bug? From QGIS 3.4.5 and 3.6 asks password repeadly to connect to PostgreSQL 10 .
It is actually not a bug. The saving of the password does work fine in QGIS 3.6. After storing the password under basic tab in the connection to PostGIS window, you will notice you will no longer get asked a password when you connect to the database, however when you open the QGIS projects the password will pop up again. So go to individual layers and using the change data source tool browse to the database with the password saved and resave the project. Once you close and reopen the project, you will not get asked the password. The repetitive password is no longer there.