Your harvest time is strain dependent. more sativa=more time in flower. If its more indica, your still looking at 8-9 weeks. your plant is pretty stalky, so It doesnt have a hell of a lot of sativa in it
(although nearly every plant grown today is a mix of sativa and indica)
Try not to get hasty. You will hate yourself in the short term for not having smoke, but in the long run you will be stoked on your yield and potency increase in the last 2 weeks.

Side note: 12/12 will maximize hormone production during your dark cycle, not by much... actually you'll probably see more of a benefit when it comes to your electric bill by going 12/12 than your plants will.
If 13/11 =13on/11off...

hope this helps...