Don:
I've added a screen saver control with a program to let me control screen saver times...
sudo apt-get install xscreensaver
However it's best to do an update first...
sudo apt-get update
followed with
sudo apt-get upgrade
After installing the xscreensaver you'll find it in the preferences tab in the Raspberry menu.
Further actual testing... With Steve's image of Buster and following my own advice of doing the update first, well after I looked at what the image with some older updates would do. There I saw some real issues with the second screen not coming up or the Pi not booting at all. So with the update/upgrade which was very large... it seems to have fixed a bunch of 2nd screen issues!
Jim Albanowski