Does Photo Stream update later if computer is offline? I shoot with a DSLR on the road and import the photos on my laptop MBP to edit them.  Sometimes, the laptop is not in a wifi zone when I import the photos (physically from SD card), and they do not get to My Photo Stream, even after I take the MBP to a wifi zone later.  

Is it because the photos are only considered "new" if the MBP is connected to a wifi zone WHILE the photos are imported?  The Photo Stream description in Aperture prefs seems to indicate that "Send all new photos to My Photo Stream."

Second question:  If I import 400 photos from a shoot and the MBP goes to sleep after a few minutes of keyboard inactivity, does the photo stream continue to update, or is the uploading activity put on hold until I wake up the computer again.  Related: Does iPhoto or Aperture have to be running for My Photo Stream to continue uploading imported photos?
1) In my experience, I've found that simply quitting either Aperture or iPhoto and re-opening is the easiest solution to a stall in the syncing process. I've experienced similar issues before. As to to the "why?" - that being "why does Photostream stall when switching networks," I can't provide an answer. But the failsafe solution is to quit and re-open the application.

2) Again (in my experience - Apple's documentation on this is sparse), I've found that photo stream only actively syncs when the machine is 1) awake or 2) sleeping, but not 'hibernating.' Unlike iOS devices, it seems as though Photostream is more stubborn in regards to OSX devices regarding the active and continuous syncing of data. 

3) Yes. Either iPhoto or Aperture need to be open.