In my observation, it checks for new content each time the screen is refreshed. So, If I'm in an article, and I nav back out to the collection level, I'll be alerted of an update, If I go from one collection to another, I'll be alerted of an update, or If I quit and relaunch (like you're sugguesting), I'll be alerted of an update - if one is available.
I've noticed, it's also dependent on your internet speed - sometimes the updates come through almost instantaneously, sometimes it may take a few minutes.
hope this helps!