I let mine grow to about 2 feet tall or so... I grow indoors so it cuts down on the space a bit... I hear it also makes for a more potent high.. How tall are your 'girls' now??
Yes about 2 feet is a general rule,,,,but,,pay attention to the strain ,,if it is a foot or so tall,,and has alternate nodal spacing,and has many chutes,,a good root system ..it can be flowered...keep in mind,,many strains can double,or triple in size when flowering is triggered....