Sometimes you want more granularity than a drop-down menu supplies. I found myself in this situation with start times for the screen saver on my Mac at work.
I use the initiation of ScreenSaver as a means to lock my machine (since Apple still ignores this vital business-environment feature). If I’m not actively using that machine I want it to lock as soon as possible. I also found that the controls in the GUI (the aforementioned drop-down menu) were too limiting.
After some hunting I found the controls necessary.
First, take a look at your current evocation time:
defaults -currentHost read com.apple.screensaver | grep idle
Mine is currently set to 120 (or two minutes). I understand that anything below 60 will default to 60 so that seems to be the bottom limit. Here is what you need to do to change your idleTime variable:
defaults -currentHost write com.apple.screensaver idleTime 180
As you can see I specified 180 seconds. Feel free to test out different times as would be appropriate to your situation. (Zero (0) means never.)
If you are seeking a command to initiate ScreenSaver directly (perhaps for scripting purposes) this works:
Thanks to this thread for most of this information.
Have fun with that.