I just tried defender mode again starting with 3 planets containing stealth battleship, shield bearers, and snipers. I set AI difficulty to 5 and 6 and did the plain old setup forcefields, tachyon, and gravitational turrets and continously adding turrets around the planets as much as my power can handle. I also control my fleet of ships from 1 planet to another depending on which swarm of AIs come first. They didn't take out any of my command stations until the part that I have already won the game.
I set the time to survive 1 hour.
The first time I tried it and set it to 30 minute with level 6 & 7 AIs, they came too swift too early and destroyed me.
Anyways, any advice on how one should set up defender mode?