So we made it to the end of the game, after having gone through two and a half decks of genestealers, and then we finished off the level 4 blip piles. I couldn't find any mention anywhere in the rules that the blip piles should refill. This left the bizarre situation where we could chill out and fill up the final location card with support tokens at our leisure - no combat involved! This didn't seem to me like something that should happen. Am I doing something wrong?

I believe you're playing it correctly. The blip piles don't automatically refill after you clear them out. However, remember that there is an event card called The Swarm that adds two cards to each blip pile. I think there are two copies of that event. And a marine can also be slain by the Psychic Assault event, so if you're down to a single surviving marine you could still lose the game even after clearing all the genestealers.

Yeah, I know I could still perhaps have spawned a couple of genestealers through events, but should the last location card ever really play out like this? To be fair though, every other time I've made it to the last location it has been much more intense. Just seems like a massive anti-climax this time round! I even had two whole space marines left!

There is a rule, that when you kill all GS and blip piles are empty you automayicly win the game, no mather the level 4 rules.

muk said:

Of course, only the Lauch Control Room matters with this one. Toxic Pumping Station you win by emptying out the formation and both blip piles and Genestealer Lair you win by defeating the Broodlords, meaning you have to clear the formation anyways in most cases (though might get straggler GS that aren't with the BLs sometimes).

muk said:

This is correct. You win if you run them out.