Your users may be, too. It's not unusual for me to open my sleeping laptop several days later and expect the open web pages to work without refreshing them.
Most of them are open from other tasks. But that doesn't make them a distraction. They're there for when the current task finishes and I can go back to them.
The alternative is to close them all down and reopen them, which is vastly more time consuming.
quick pjax e.g.:
<html data-lastupdated="1234567890"...
$.getJSON('/lastupdated.json', function(lastupdated) {
if(lastupdated > $('html').data('lastupdated'))
{
$('a[data-pjax]').removeAttr('data-pjax');
}
});