Once the humans figure out the base game, not only does it become bland, but the cylons won't really stand a chance, save for a lucky break in CAC or something.
My experience runs contrary to all the wisdom I've seen regarding this game.
I've played 5 games now, and its always been 4 humans vs 2 cylons.
We tried the sympathizer once, and it was a crushing cylon victory.
We tried the "no sympathizer" once, and it was a crushing cylon victory.
Three times we simply tried 4 humans vs 2 cylons, no adjustments at all.
Those 3 games each came down to a single turn deciding which side was victorious, with the cylons winning 2 of those.
I believe that the issue is one of spoilers. I suspect far too many people come to a site like this and "learn all the tricks." At that point, the humans have an advantage. But if you get 6 people together who have never played before, and each is trying out their own strategies to see what works... the balance is in favor of the cylons who have far fewer variables to deal with.
It may be too late for most to close the barn doors, but I think the greatest journey with this game is to not read tips (like this one
and let the game evolve over time.
I'd weight your first games in favor of the humans. Over time, it balances. Eventually, you need to weight in favor of the cylons. I think that evolution provides great replayability. And you can see for yourself how the odds evolve, and make minute adjustments appropriate for your own group.
Add expansions slowly, only when you get grumblings of boredom.
I think one can come up with endless scenarios to try out for free, which both balance and add freshness. Here's one:
Galactica starts with a permanent damage token on the Weapon's Control. It's a gaping hole in the side of the ship that cannot be repaired.
Now, your balance shifts back to cylons. You increase the chance of that rare "Galactica Destroyed" end game. It makes all players shift their playstyle, which is a great positive for those who have reduced the game to a routine after a hundred plays. And nobody has to play that dreaded "even man role" that is less fun. You push the balance back onto the gameboard which is just happy to be unboxed.
And in the end, I find each journey enthralling. I care about winning in-game, but once it ends, I don't care a whit if it was unbalanced. I had the time of my life trying.