I regularly use two devices and don't always logout from Perl Monks site when leaving a device for a while

No, there is no harm in that. In fact, there's no reason to log out from perlmonks, ever (aside from the obvious things, like - you logged in on a shared computer somewhere). The site doesn't care how many devices you're coming in from. The site maintains no sessions with the browser. And the only cookies (normally) that the browser holds are strictly for "being logged in".