dear length hardly matters atleast in subjective questions of css but ur valid aruguments n analytical skills r measured in almost all papers...its not an secondary school exam wher quantity matters n not da quality...n ther is no rule dat u r suppose to write say 8 pages or 10 pages for a 20 marks question if u write valid arguments n all points covered in even 4 pages u wil get a gud credit whereas if u rite even 15 pages for any particular question but irrelevant u wil get nuthin ...
same goes for essay bt normally they give words limit of 3000 to 5000 words for essay which is equivalent to 15 to 20 pages ...