Why he wait so long???
That is the question I have had in my mind since I knew it was Walter...nate who was doing all these things in our side... why he waited so long to take his son back... I mean other side appears like they have best technologies so they would have created a portal to our world years before... and also I donīt think Walternate only wants to destroy our world for vengence... if he has to revenge on someone that is Walter not the millions of people... he only has Walter to make him pay all the pain he caused to him and his wife by abducting Peter... not us... so, I think there is more than that... he thinks we are evil and wrong... why?
I guess three reasons, first he had to build one, which might have toke some time, second of he's a busy guy I guess at random times he might be like "time to check up on Peter".Third of of all he was waiting for the right time, like when ever he checked on Peter. Peter might have been talking or doing something.So it was not into he checked in on him, and he saw Peter was alone, and not doing anything just listing to music.