How to Balance WW games.

[matrix]

I am in the process of writing up a theme idea for an Average Speed game I'd like to mod sometime later.

It's generally accepted that a 13er

3 wolves - 1 seer (n0 peek) - 9 vanillas is balanced (?)

I think.

Once games get larger and more complicated is there a formula for working out how to balance things fairly?

Are there any resources I can get pointed towards that detail how to setup games so the balance is goot.

Obv you can just rand the game and trial and error through a bunch of scenarios to work out how long any given setup could last but.

What makes a game balanced?

What effect do various Mish Mash style extra power roles have on a game?

And how long should a game run for at most? 2weeks a month?
(assuming 12 hour days & 12 hour nights)