Hello xxfunguy007xx2000
How long you should SD also depends on some other factors, most of which we probably can't come up with a clear, empirical formula to apply to each possible scenario.
However, we have a few tips at our disposal as long as we remember some details:
1.) First, we SD because we want to decondition our muscles. Our muscles get conditioned (that is, adapt to the loads we lift) because of our training. Therefore, it is generally true that, the longer your cycle, the longer you have to SD.
2.) Our SD makes the muscle decondition (unadapt) because we refrain as much as possible from "using" the muscle - that is, exposing it to a significant load. Ideal SD would probably be lying down motionless for the entire duration of SD, but since we have a life to live, we just go with what we can manage. So generally, the more active you are with activities that present almost regular and significant strains on the muscles, the longer you would probably have to SD.
3.) You generally cannot SD on an "installment" basis - that is, if after merely 5 days you suddenly had to exert a muscle group(s) to a condition similar to a moderate to heavy workout, you generally can't just forget that happened and SD for the remaining 4 days (if you scheduled SD for 9 days for example) and expect the muscle group(s) involved to have been deconditioned as adequately.
Hope that helps
-JV
