the more times you study, the more times it gets hammered into your brain ... thus you are able to quickly recall it when you study again! *nods*
the time taken to memorise something decreases each time you study (effectively)
pre-hsc study period is after term 3 ends until the day before the first hsc exam starts, according to my sis who did her hsc last yr, basically the holz after term 3 are meant for studying