20 nobles is fine. You can have 20 nobles.
We're worried about people have 50 or 100 nobles, or more.
It's hard to play a 100 noble faction. Your strategy may demand
that you continue expansion if possible (especially if your
enemies continue to do so). But dealing with 250k turn reports
can leech the fun out of the game. I still have visions of the
end of Oly I, when players stopped bothering to give their nobles
decent names. "Exploration scout 59". >shudder<
-- Rich Skrenta <email@example.com>