How to win if you are up against mobile rulership?

Hey All

 

So I have been playing the Huge maps with all set to unfair. The problem I am having is playing against a mobile rulership.  We get down to the last two, and I still don't have the whole map unveiled as scouts just cant make it through it all. I do however see the opponents home world. So I go and destroy it. Game is not over because of mobile rulership. 

Now I still cant see all the planets, and because they are the last standing faction, they own a lot of planets, most capable of building more ships. So how do I FIND all their rulership ships and destroy them? Even if I can find them, I wont be able to take them down faster than they can build them, also at multiple planets! So how do you win?