In a good game liberty will usually finish 36-45 turns before finishing the game. In a good game, the final policies will probably take 5 turns each (with perhaps the occasional one taking 6). Utopia takes 1 to 5 turns (though I never managed 1). In what I assume is the most common strategy, you will have one full policy branch and one or two policies from an almost finished policy branch to complete. This means 7-8 policies plus utopia, i.e. 36 -45 turns.