This sounds like a cookies issue. So far I'm not having any problems like that, but then again I've been doing other stuff on and off today.
If you set your browsers to allow 1st-party cookies and either deny or request permission for 3rd-party cookies, you should be OK. (I use DENY 3rd party myself.)
There is another problem that could cause it. Flush your cookies for anything older than X (where X is a week or two). Sometimes you have a limit on how much your browser is allowed to keep in files and depending on exactly how that is configured, it might be dropping recent login cookies. I have an auto-cleanup set for old cookies, so every now and then I'll get a "please log in first" notice. But I haven't had the "kick out" problem recently.