I discovered to my astonishment at the first glance that my thinking of how session cookies behave on mobile devices is overruled by reality.

On normal desktop browsers the behavior is to store a session cookie as long as the browser session is active. The session should be closed, if the last browser window/process is closed. 

Now on mobile devices you hardly ever close a browser app, you just send it to the background. 

I discovered on my Sony Xperia Ray with Android 4 that the session cookie is not expired, even if I purge the browser process. But on a Samsung Tablet device it would. I don't know, how iOS devices behave in that way.

This is a problem!? What should I do to work around it? 

For now, I decided to let the cookie expire in one day. But I'm not very happy with that.  

Should I lower the lifetime? Perhaps to 8 hours?