The short story is: The time between adding rennet and cutting the curds determines moisture content, (among other things) eventually, of the cheese. Most recipes vary according to the style and type of cheese (if it is a dry cheese, such as a parmesan, you cut it sooner. If it is a moister cheese, such as a brie, you cut it later) and have definite guidelines as to when to cut the curds. For a blue cheese you will be cutting the curds within 30 minutes to an hour or so of adding rennet depending on the condition of the curd and how long it took to get a clean break.
Huge difference between an hour and 8-12 hours....if you want a successful blue, then do not extend make times such as that....