What he means is that you can delay the VC screen from popping up by saying the faction also needs to take X number territories.
Frex, from BI's descr_win_conditions.txt:
saxons
hold_regions Tribus_Saxones Britannia_Superior Belgica
take_regions 18

Therefore, the Saxons in BI have to have Tribus_Saxones, Britannia_Superior, and Belgica, as well as controlling 15 other territories (for a total of 18). So you could, say, for the Casse, have whatever territories you feel they MUST have, and then add a "take_regions X" for the rest. That way you don't have the VC screen popping up too early.