I find this whole thread confusing, and people giving advice that are also confused. I do not believe that SOG has anything whatsoever to do with a perpetual harvest, although some people grow a SOG and a perpetual harvest all in one.

SOG does not mean to harvest every two weeks.

SOG is simply growing the smallest possible plant flowering in the quickest possible time.

Your chosen method of growing, be it dirt or hydro, has nothing to do with SOG, and sexual maturity does not take 6-8 weeks, if it does, theres a problem you need to investigate further.