PPG, I have not seen this issue and I keep SCF open virtually all day long. I have noticed that when I click on "Hot US Auctions' in the left hand menu, it takes me to the page as 'Guest' that makes it look like I need to log back in. But I am actually still logged in (I can click on any other page link and am still logged in).
I will try that if I get "guest" again. I may have but am not certain but will make sure if there is a next time.
I use "restart" normally. I use shut down when I am actually not going to use the computer for a day or more. I also manually close everything open then hold down the power button to turn off the darn thing once in a while.
Edit: I am on a laptop with Windows 10. Have not logged on with the Apple Desktop.