Actually, I’ve just thought about this issue further. And, I’ve uninstalled Stay Alive! Because, I’m worried about the security implications.
Normally, I use my Chromebook at home. So, having to retype my password every time I take a break, is inconvenient. But, I also take it with me if I expect to work. Consequently, having the screen unlocked all the time could be a security issue. Though I realize that I should close the screen, there might be circumstances when I forget.