I used to have a couple friends that I'd load up a Hamachi server with. The four of us would jump onto the biggest map available, or use the map editor to create the biggest one we could.

We had epic matches that could last for days. The multiplayer save feature was awesome, as we'd have to save and leave and come back every so often.

Those tended to drag on and get boring fast though. Just too much territory to effectively manage. I don't think we ever actually finished one of those matches.