Many times if I'm taking a quick break from something I'll log on and if the home page does not indicate any new messages then I immediately log off. Then hours later I'll log on, still no indication on the home page of new messages but I'll have time to poke around the forums - and the minute I get to the main forum page I'll have a new message indicator. It wouldn't be so annoying if the SLS date/time stamp didn't indicate that the message had been sent prior to that short break hours ago when I logged back out because the home page didn't show any messages.
Rarely are my messages here time sensitive - if I've gotten to the point where a meeting is imminent then we've usually switched to other methods of communication. But it's just one of the many reasons why I offer alternative contact methods soon after deciding I'd like to exchange messages/arrange a meeting.

